On a hot summer day, with transmission lines sagging from a combination of heat and load, a Van Hool double decker bus would likely encroach on the safe clearance engineering standards of existing transmission lines. A little wind, and...... The 2003 Ontario blackout was the result of a transmission line contacting an untrimmed tree, in Ohio.
Roads require light standards, maintenance (ie cranes), light bulb replacement trucks.... further potential encroachments.
A fallen transmission line snagging a bus, or even just blocking its path, is plausibly a 1 - in - 10 year occurrence, which is likely too frequent for most actuaries. Insurance would be problemmatic.
Busses do slide off roads in winter, potentially contacting pylons.
All of this can be solved with money, but that's what will hold this back.
- Paul