AT fire in an assault hex

[plloyd1010]

The parsing came in this sentence from 12.52, which begins:

They may conduct Anti-Tank Fire attacks ...

It never says it is in conjunction with, or part of, assault combat, merely that it can take place in the hex.
Then where was the question of how much AT shooting could actually take place. OP fire doesn't allow normal fire. Should firing defensively while assault combat is taking place allow normal fire when assault combat might be happening again? We decided no, it was just too much shooting for the gun.