Since when do you need eminent domain to buy a bus?

Did you read the article? One of the big issues that some cities are facing is finding real-estate for installing charging stations of sufficient capacity. It specifically cites Philadelphia as having run into this problem.

This doesn't stop them from copying what China does.

China has the same problem in Shanghai. The solution they use is overhead wires to charge busses while they are driving for parts of downtown that busses can connect to and disconnect from at will.