We have the bus shelter problem in the UK, too. Our research has suggested that one of the reasons it happens is a side-effect of the shelter manufacturers using toughened glass panels. Also use in car windscreens, toughened glass is designed to beak into very small, relatively blunt pieces when broken. Unfortunately, for vandals this makes for an impressive display when they strike a bus shelter glass panel with a hard object.
One way to counter this aesthetic experience (a significant reward for the vandal) is to coat both sides of the glass panel with a thin plastic laminate. This is easily done and is relatively cheap. Now when a panel is struck, the glass will still break in around the area it has been struck, but is held in place by the laminate. There is no longer the ‘crash’ of the glass breaking and falling to the street, and so the motive is greatly reduced. Such ‘impressive display’ factors are important when considering acts of vandalism undertaken (usually) by a member of a group, as their desire to ‘impress’ their peers is an significant motivator for committing the offence.

Hope this is useful.

A.