All quoted rules are from v1.2b of the rulebook.
From Transport Special Ability (p. 18):
On p. 18 in the section on Transport ability, DPG wrote:
A unit inside a vehicle cannot be targeted and is not hit by blast patterns.
So it seems reasonable that a unit inside a vehicle cannot be targeted by an assault. That is clarified in the other thread.
Do note that friendly units inside a vehicle (that have been given an order) can assault out, assuming the vehicle survives of course
On p. 8 of the Vehicle rules, DPG wrote:
An assault can only be launched from a free space or a space belonging to a friendly vehicle with the Transport special ability (see p.18). It must be adjacent to the defender
If the vehicle is destroyed during the assault:
On p. 18 in the Transport ability, DPG wrote:
If the vehicle is destroyed, the troops inside take no damage, but must be redeployed on empty spaces adjacent to the wreck.
Units cannot be redeployed on spaces occupied by other units.
They can not be redeployed in a space within an enemy ZoC.
The units’ owner chooses where to redeploy them.
Place a Suppressed marker on each unit.
Any unit for which there is no available space died in the explosion.
On the subject of the Surprise card, the card is limited to only windows of buildings according to the card text. You and your opponent can certainly agree on house rules to the contrary, but that is what the card states.