Alien Spawn Information (thanks to TSTOTopix)

Okay, so just tested it again.

Opened up, let the aliens congregate, then squashed them all. Again got exactly 50.

I tried to open up the bank by going to KL and returning, but that didn't work. Then I exited and checked back in 30 minutes, but only got the 6 new ones that spawned in 30 minutes. Checked back again another 45 minutes later, but still no bank of 30 -- only the 9 new ones that spawned in that time.

I'm inclined to think the bank is similar to the Easter bank -- it was written for, but doesn't actually work. Unless going to KL made me lose all my aliens, similar to how going to KL wipes out gremaliens (?) and cleared raided houses.