Sacramento/Yolo Transit is using electric buses for a Davis Flyer between UCD hospital/downtown Sacramento and Davis/UCD main campus. No hills, obviously.

IIRC Foothill Transit (or is it somebody else in SGV?) uses electric buses for El Monte-downtown LA bus lane commute service. Unless you're very careful about routing, there *are* hills in downtown LA.

Don't know if they still use them, but AC Transit had electric (fuel cell) buses for many years. Probably didn't use them in the steeper hills though.

Electric (battery) buses are becoming pretty much stock items among bus builders. Yes, they probably have limits in terms of hill climbing, but most buses do; not unusual to have diesel & natural gas buses with specific gearing for routes with steep hills unless (as with the Muni's fishbowl GMs) the company is willing to pay for an overpowered drivetrain. Yes, they have relatively limited range, but in properly chosen service they should work fine.

Cost of operation for electrics is likely less than for diesels - especially regarding drivetrain maintenance work. Ask the Muni - they've had electric (trolley) buses for ages (almost 100 years if you count the early Market St. Railway lines). The capital (purchase) cost difference probably more than makes up for that, though.