I don't think there is any reason for Waymo not to pair up their system with a regular petrol car. Electric vehicle capability is orthogonal to self driving.
Depends, if they are planning to run a taxi fleet or restrict themselves to new personal vehicles, integration and operational costs for ICE vehicles is likely going to be higher than EVs in a couple of years. There is little common between the vehicle dynamics and control for ICE and Electric vehicles, and it might be more practical to focus on one platform.
