Hmmm, well Madfred, you are right, I would like a more reliable solution, and I need the troops to move and engage the ambushers too.
I don't know if that would work, the convoy seems to be moving fairly quickly, and if I eject them, there more likely to die from the speed of the convoy, and if they even managed to survive the ejection, would likely get themselves run over but the following armored vehicles.
I will try what is suggested here, but I think a more reliable means will be nessasery.