Building tram tracks or electrification sometimes does not work if there are buses on the road. If there is a bus at the place of the second click tram track construction does not work. While this is, of course, in a way realistic, it is possible to build 'over' buses, i.e. by clicking before and after the bus. Only the tracks cannot begin or end where a bus is standing, thus I still consider it a bug.
It is a know bug. I will have a look though.
EDIT: Will only happend with tram tracks, and is not really easily solvable without other side effects. SHould never happen with electrification though.
I'm sorry, you are right, doesn't happen with electrification.