Electric bikes have a tough time with hills. That would be the only part where I would say gasoline is superior to electric bikes. Well, it would depend on big of a hill or mountain that we are talking about. If the hill only lasts about 1 or 2 miles, I think it's doable.
I think the Ezee kit might be something that you should look at. Also, consider the fact that if the hill is very long like 4 or 5 miles, you need to think about whether or not the motor can handle the heat generated.
Actually, they can recharge going downhill if you use the brake. There are bikes with regen that replenish some of the battery when you use the brake. I've heard that it doesn't replenish all that much, though.
If the hills are steep and long, I would recommend a gasoline powered scooter.