Was coming back to edit my comment and say this, its a stupid mechanic.
"Oh you just wasted your tank(s) to take down X tank?" Shame you chased it into their base and it was only abandoned!
https://youtu.be/lJR8aq48WU4?t=24m10s
On Topic:
Lower Pop cap and fuel cost for Brit AT emplacement
Basically this game needs a lot of silly RNg things changed to work on basis of skill, and abandoned doesn't happen because you're skilled unless you play USF, in which case you can tactically disembark to force attack ground and save vehicle crews. This is ok, but random abandon just needs to go.