From the release notes: "Apps that offer routing information, such as turn-by-turn navigation services, can now register as a routing app and make those services available to the entire system"

Makes me hope a 3rd party transit app will be able to provide routing information in a format the default maps app will be able to display.

I would love Maps to be able to mash together the data from 2 or more routing apps in order to give me a complete journey!