If they have their own fleet they can generate their own (historic) traffic data e.g. via Map Matching and use an open source routing engine like GraphHopper with OpenStreetMap data. (disclaimer: I'm one of the developers of GraphHopper.) It is unclear to me whether their current practice is in harmony with the Google Maps TOS. For some places there are also open traffic data sources: https://github.com/graphhopper/o…
But I'm not sure if it applies to this use case.