Is the upgrade selectable or randomly selected?

Or does it damage/destroy all upgrades in the province?

If trying to destroy an air base... Would you happen to know, if the province had a disabled barracks also, would that drop the chance to 50/50.

I'm looking for a counter strategy. If you only have an air base in a province, 2000 gold, destroys that airbase and grounds your planes.

Just asking, cause I thought it was a neat move when some spent the 2000 gold to disable my air base and ground my planes.

Thanks for the knowledge, spies are getting very interesting, besides seeing whats in a province.