[ezmaass]

So I took a quick look at the documentation I could find here. Looks like in the US there are two systems:

1. RTTI (Real Time Traffic Information)
2. ARTTI (Advanced Real Time Traffic Information)

RTTI appears to be similar to what I had on my 2007 335. It's FM radio based, and as AP pointed out it's less frequent (and often less accurate from my own experience with it).

ARTTI is only available on "select 2013" and newer vehicles. My 2014 550 has it. It's a component of the BMW Assist services, as I thought. It relies upon the cell transceiver that's used by your other BMW Assist and ConnectedDrive services. I think each new car gets this for some number of years, and afterwards you need to pay for it, but I think it's a relatively long time (10 years?).

Also confirmed from the documentation I read, ARTTI does update every 3 minutes. I'm very glad BMW kept from integrating any of these services with Sirius... what a complete bamboozle that Audi makes you pay for a Sirius XM plan just to get your traffic info!

So, there you have it.