I don't know if this is calculated from the centre of the vehicle. With grid activated in cheat mode you can see it is only 45 sight range from the front of the M8 and 55 with vet1. This makes scouting pretty dangerous if there are AT-Guns or JPIVs with their own scouting support around.
Vet 1 m8 has 60 sight, not 55. at vet 1 it gets +20% sight range. 50*1.2 = 60.
The vet 3 +30% is weird, as I've never seen it get that bonus. Could be a typo, could be bug (like sight ranges bonuses not staking).