I tested this offline so I'd know how to file the bug report. It doesn't dump - it just sits on the other team's refinery dump spot forever, possibly blocking the AI OT on the team with the working refinery from dumping. On the way there it is also likely to ram the enemy OT and get stuck though - you'll often have to help it out by ramming one of them away for the OT to actually reach the opposing refinery.
I'll have to go see what the truck does on large maps where the pathfind grid isn't complete enough to connect the 2 bases together. Because in that case it certainly can't drive to the enemy refinery.
e: it just sits still on its own ore field forever after collecting. Which is honestly what it should do in all cases. I have no idea why the ore miner script tries to seek out enemy dump zones if they're in range (it even knows they're enemy ones, if it didn't then it would actually dump at them!). It's not my script.