I believe TomTom uses the same kind of crowdsourcing data approach to its HD traffic system, but only uses Vodafone SIM card data so won't have as much data as Google will do.
TomTom also uses ITIS data (traffic camera data, police info etc) and also uses data from some car manufacturer sat nav data for connected vehicles (not sure which manufacturers).
Like you I'm always trying to find the best source of traffic info .. I've got TomTom HD traffic on my iPhone, but overall I find Google Maps has got more accurate traffic info .. But TomTom has better overall routing algorithms using their IQ routes data...
In my experience anyway
