If an ebike can go fast enough riding in regular car lanes shouldn't be too much of an issue. It wouldnt be any more dangerous than driving a motorcycle.

The main reason bikes don't do well in car lanes is because they can't keep up with the flow of traffic typically and cause cars to pile up behind them and then people get impatient and aggressive.

An ebike that can go 50-60kph would basically just be a motorcycle in traffic that could then slip into a bike lane when traffic gets bad.