MSN gas prices


i am wondering how this gets reported ?
how are gas prices posted using the MSN cable - is it done by radio trasmissions or by individuals reporting prices ?

marnoldi Nuvi 680 & Nuvi 2797LMT

And how accurate are they

And how accurate are they usually? One of the reasons I'm thinking of upgrading my GPS unit is to have the ability to see gas prices. But if they are just as inaccurate as the built-in POI data, it might not be worth it.