Electric buses have no problem with having the potential tractive effort to climb hills, look no further than San Francisco and Seattle. Battery buses have additional problems with inadequate amps and battery weight. Battery technology is advancing, and this is becoming less of a problem. Tractive effort is not the problem, as much as how hills will affect power consumption, and therefore, vehicle hours of operation, without the need for additional charging.

If you want the all time failure for transit bus at hill climbing, look no further than the fleet of methanol buses LA bought in the 90's. Supposedly cleaner (they weren't) methanol lacked the to power density anywhere near diesel or CNG, necessary to climb even the easy hills of downtown LA, and all were out of service and scrapped within less than a decade.