Electric buses are nice to have, but they seem sort of performative. For the same cost we could simply increase the number of buses and eliminate people driving their children to school alone.
So it's unlikely there's a valid case to be made that the cost of electric busses would be preventing expansion of public transport.
Which means operators only care about annual operating, insurance, maintenance, and finance costs. The total is important[1] not the relative amounts. If electric buses are cheaper on an annual basis and can handle the route, those guys will buy them. (Accountants are going to accountant)
[1] The opposite of people who buy personal cars who focus exclusively on capital + finance costs and ignore insurance, operating and maintenance costs.