I think if the computer uses a team up, and u have an open TU spot then u get that TU
Or more logically, the team-up that the enemy team uses should have a chance of dropping at the end of the match, same as the chance of getting one from one of the enemy characters.
I think team-up drop rates need a slight increase - not so much that they drop after every match (as that was frustrating and led to constant inventory management or “you don’t have space for this awesome team-up, too bad!”), but now I very rarely get them at all.
…consequently forcing me to request team-ups from my alliance, increasing the chance that my alliance members will pay HP to get them back early… damn it Demiurge, THIS WAS YOUR PLAN ALL ALONG!! 
There’s a nice way around that by using 1*characters.
https://forums.505go.com/discussion/21472
Or maybe get rid of team-ups all together…I love holding back Wolvie until I know the opponent cant attack and then POW! I get hit with a whopping 4000 point hit from a team up I didnt know existed… fun…