Troop Accelerators were DLC from I think June, but they are definitely the most rare of all the AI special ships. They will be a tad more common now, but still quite unusual.
Oh, I didn't knew that! Do they actually give the AI additional units from nowhere(and so giving the AI an advantage), or do they suck reinforcements that could be used elsewhere?
They give them additional units "from nowhere" -- they are quite nasty, and hence part of there rarity!
Yes, that just takes time for compiling them, and so it tends to lag a bit. Rev has been doing that for me so that I don't have to spend an hour or more of CPU time on my own computer to get them there, but eventually I'm going to be running those simulations a lot more in order to get the new ships better balanced than they currently are. At the moment, the new stuff is all very much "rough draft best guess." 
I wasn't speaking of simulations, but just somewhere to see the current multiplicators of the new units (for instance, bombers have x80 against fighters), so we can know witch units are resistant to the unit attack, and witch ones can kill it in one shot. Something like we can see in this page, but with the expansion units. I have mixed feelings against the simulation myself. Does it truly represent the capabilities of each units? I'd rather see a general "strong vs and weak vs" help in the tooltips and see the simulations elsewhere. But it's just my opinion.
I've written at length before on why the simulations are valuable, even if the entire concept of a simulation is flawed. But the short version is that the internal bonuses are extremely misleading. For example, many of the new ships have bonuses against nothing. So then what? The simulations give you data about all the various factors that create a natural rock-paper-scissors-lizard-spock-AI-War interrelationship between the dozens of ship classes, whereas the specific bonuses will only tell you where that relationship has been explicitly augmented.
Basically, the simulation puts some guys of one type against some guys of the other type and makes them fight, and records who won, how fast, and how much health the winner had remaining at the end. It's not perfect in that it doesn't account for fleet mix, range overly well (ships start out close together), or clever tactics (ships just attack each other on autopilot). But, I've experimented with a variety of things in the past, including just showing people the raw bonuses during alpha, and those always were super misleading because there are so many variables that go into the combat, and no human can quickly calculate them all (shields, attack range, attack power, health, various special abilities, various bonuses or penalties, etc).
Anyway -- if you want to see the bonuses, however, you can always get that data by starting a new game, hitting F3, and then hitting Ctrl+Shift+F8. That will export a variety of data files into your Data folder under the game directory, and is what is used by Revenantus to create the wiki pages you're referring to. You don't ever have to wait on us to have that info at your fingertips!
