Mechanised Infantry can enter building hexes using 2MP as per TW page 168.
Can they change level inside those buildings? e.g. as per infantry 1 MP per level?
As their movement is limited by their motive type e.g. tracked, wheeled, etc and vehicles can't move up inside buildings I'd say no.
It's a shame there's no official advanced rule about Mechanised Infantry "getting out" of their vehicles and converting to foot movement (we tend to house rule this).
