I'm trying to compile a guide on everything one would need to know about the Espionage system in DA/TA, so far, here's what I got:

First off though, props to jpinard for his DA guide, and for this post the page on espionage.

Intel Levels:

Low:  5
Medium:  15
High:  43
Advanced:  147

Those are totals, not how many more you need to get to the next level.

Spy-weeks: each week a single spy is planted on a planet is 1 spy week.  If multiple spies are planted, then multiple spy-weeks are accomplished.

Example, if you have 15 spies to use and placed them all on the same race w/o ever placing them on a race before, you should get Medium intel level that next turn.

The +Espionage skill:

-the +Espionage skill seems to only affect the amount of money you spend to train spies.  Unlike research/social/military bonuses that you only pay for 1/2 of the bonus, espionage you pay for all of it.  Whatever your +% is, you'll spend that much more money than what the slider would have been for a race w/o the skill.  So a 1,000 bc income race with +0 set at 25% would spend 250bc a week, a race with +50 would spend 375 bc a week.  The effect of this skill and tech stealing is still not known to me...give me some more time.

Spy Costs

When there is only 1 week remaining to train a spy and the funds devoted to training exceed whats required to train the spy, the balance will be refunded to you the next week.

I tried to find a formula for the costs, to just post that up on be the end all, well...that ended up not being what I was seeing for a pattern.

The first spy is 100bc, it escallates to 180bc by the 5th, then has a huge jump at 6th, 10th, 18th.  With those exceptions in mind, the rest were pretty much just a 1bc increase in cost change.  To give some milestones, 25th spy, 2,975bc, 50th spy 5,230bc, 75th spy 8,165bc, 100th spy 11,650bc.

In my test, the overall cost for 100 spies put me to 554,644bc

For average Joe Spy User, I'll post the first 20 spy costs:

1-100, 2-109, 3-127, 4-150, 5-180, 6-710, 7-745, 8-785, 9-822, 10-1167, 11-1215, 12-1260, 13-1315, 14-1367, 15-1422, 16-1480, 17-1540, 18-2499, 19-2562, 20-2628.

By this point, it's a very linear change in cost.

DA 2.0/TA 2.0

1 large change has happened to espionage in 2.0.  Now you can passively spy on a race.  This is done by devoting a spy (up to 4 per race) permantly to a race.  In order to reach each of the above intel levels, you must have 1 (low), 2 (medium), 3 (high), or 4 (advanced) spies placed to reach it, as well as the wait time to accrue spy-weeks.  This passive spy system is now the ONLY way to get intel, agressive/planetary spies won't gain intel anymore.

For example, if you only place 1 spy on the Korx, 5 weeks later you'll hit Low.  If you don't change the number of spies allocated to them, then even if you wait another 10 rounds, you won't see Medium.  Upon placing the 2nd spy, you'll start acrruing spy-weeks again, at the rate of the number currently placed.  So in this case, placing a 2nd spy on the Korx after hitting Low will net you 2 spy-weeks and thus hit Medium in 5 more weeks.  Nothing is stopping you from dumping 4 on the race right off the bat and forgetting about it, but I just wanted to point out the thresholds.

Also changed in espionage is the ability to spy on minor races....hellooo dread lords, gimmie your tech!!!

Version Bugs:

-2.00 thru 2.02 Any passive spies on a race that gets destroyed, will perish, unlike planetary spies which get refunded to you.  (Bug confirmed in 2.00-2.02, a fix should be in place for 2.03)

Other FAQs:

-Planetary spies will temporarily shut down an improvement.  Some wonders/trade goods effects however don't seem to be affected by the shut-down.  Once the spy gets nullified, the building is fully operational again.  In the case of farms, the next turn after being sabotaged, the population cap that it provided will be gone and any excess population will die off.  Once that spy moves on/is nullified, then the population begins to grow again like normal.

-Best way to avoid spies being nullified is either move them around constantly, or better yet, send them in a lrage wave(like 12 or so).  Some will be nullified, but the AI doesn't seem to stockpile spies and will have to train new spies slowly from then on.  Target their economic buildings/farms to har mtheir income since spy training is linked to raw income.

-Any of your planetary spies on a planet that you aquire (by any means) will return to you.

*edits*
06/26/08   Re-confirmed Low and I have a non-range number for Medium, High & Advanced.  No comment on a +Espionage race yet though.  Once I reconfirm those last three, I'll move onto one of those races.

09/27/08   It's been a long time, but 2.0's beta is now out so I'm rekindling my look into espionage.  spy-weeks have been nailed down.  Right now b4 I hit the hay, I have spy costs up to the 37th spy, hoping to hit 100 before I calc.

09/28/08   Found answer on destroyed race & passive spy question.  I got first set of spy costs (up to spy 100), nothing on this will get posted until I go thru the espionage skill check since I want to collect these costs multiple times to confirm.

09/29/08  I added the effect of the +espionage skill to the OP.  Nothing else ground-breaking to note right now...just a ton more turn clickings and cost tallying.  Man I'm enjoying my dual monitors right now.

10/08/08  Well, I re-named the thread finally..."Espionage Intel Levels" just no longer fit the scope of this thread.  In doing so, I re-formatted a bit of the beginning of the post.

12/04/08  I need to revisit my last comment about passive spy loss now that we can remove passive spies.

12/07/08  Added Spy Cost section and added confirmation/bug report of passive spy loss.

12/15/08  Added info about 2.00-2.02 bug of passive spy loss

12/18/08  Added link to jpinard's DA guide as well as a FAQ section (which will get updated as I see questions asked on the forums)

06/05/09 Post spy cost information.  After a year of working on this project...I think I've completed it to my point.  Any future edits will be game version related.