looking great so far, style is awesome, the potential even better. Looking forward to more - a couple of pointers...
bridge/tunnel could be much more intuitive from the normal build track/road system - just allow normal mode to go up or down with the zx keys rather than switching modes with b and t. It would also work for conveyors (see below). So if you are making a road up a hill and you want a tunnel - and it auto created a ramp - just press z and it will start to dig down or dig in if going thru a hill at the same height. If you are on a level and you want to rise up - just press x. easy.
bulldoze mode keeps catching me out and bankrupting me early game. Why not have a bulldoze timer? if you say built something and it has only been in place for a few seconds and you buldoze it because you are a noob and didnt leave enough space, you get full refund to help. Then if you also leave bulldoze on by mistake too (like I keep doing) whilst going into other build modes like rail then you click a building you want to look in that you just built, and darn it - you destroyed it again, by mistake because bulldoze was still on - you won't get penalized for it too much.
Why can't I build a conveyor bridge round a corner? - goes back to having a more intuitive build mode as before. 3 blocks high should easy pass over a station but it doesn't!!
Don't auto landscape fill under a bridge when returning to normal mode - im building a bridge!, if I want to fill it with terrain I would do it later! not my instinctive choice whilst mid bridge building