How to enable traffic information along a specific route in Google Maps V2?

Google Navigation shows the traffic layer only for a given route. With GoogleMap.setTrafficEnabled(true) I'll get the traffic information for the whole map.

I know how to draw polylines for a route from Google Directions, but how can I turn on the traffic layer only for that route?

Can I get traffic data from Google Maps?

Many existing and emerging surveillance systems are currently used to facilitate traffic data collection. Google Maps is a web mapping service that leverages GPS crowdsourcing to retrieve accurate traffic data verified by both the research community and industry.

Not possible as of API v2 version 3.1.36. You may want to post a feature request on gmaps-api-issues.