How to unlock
Completely damage a brand new Type A-469 with a Type E-7310.
It seems like you have to do all the damage in one hit, or at the very least do all the damage without the A-469 taking any damage from falling over, hitting terrain or other causes. So the easiest way to do this, is to get the middle garage on Coast, place the A-469 at the bottom of the hill with zero damage, and just charge the E-7310 straight down into it from the top. This way you should do at least 3-400 damage, getting the achievement. And probably punting the A-469 into the river, which is also cool.
This is easy to do in Flood on the road you start out on. Starting with these two trucks, point the E-7310 to the slight downhill toward the A-469, give it enough space to get up to full speed, and one solid hit to the A-469 will do it in.