havn't got the game handy to check, but i think the tooltip SHOULD tell you which units it affects. mouse over the tech, and you shoulf get a tooltip that reads somthing like:
"cas: ground attack +15%
tac: ground attack +15%
Int: ground attack +15%
Ftr: ground attack +15%"
if it does not list TAC, then it does not affect tac bombers.
however, if it lists no units, just the mission (as you say) then it upgrades that mission, and any planes attempting that mission get the benefit of it.