Do they really have to be planted on research facilities?
Did not know that ... I always thought tech stealing would still be like in DL, where you came to steal a tech once you had all info on the civ. Either way, I do not recommend you to use spies to steal tech. That is far too expensive and you will need all of your spies to defend yourself against the other civs, spying at you.

The most efficient way of stealing tech is by conquering a planet. Though I have to admit, I mostly get the worthless tech of the weapon branch I am not interested in.

"Sir we have attacked Lasitus II with our Photon Torpedoes and Advanced Troop Ships. We have conquered the planet and found something very interesting."

"What is it?"

"It is a device to make fancy light shows, mostly harmless, unless you get it into your eye. They call it Laser III. Some time ago, they equipped their ships with it."

"You mean the ships we blew away just before landing here? The ships that were not even able to make a dent into our intergalactic licence plate?"

"Yes exactly. Isn't it great that we have that stunning new technology now?"

[Captain uses Laser III to play with his cat, who likes to hunt down the little laser point.]

I was playing TA so maybe that changed because there were never any steals unless I had them on a research building? Again what stats affect them. I heard that luck does but what about the others?