CANBus GNSS Master fron ardusimple, educate me

Seems like a new product. No documentation on the site, but it looks like it can feed gps data from the receiver to the canbus?

If so, every canbus?? (I am dreaming of using my rtk3b in JD autotrac)

Canbus is a form of communication. To use it with John Deere, you would have to figure out the codes for all the communication. So yes, it’s possible,Agra-GPS has done it. But if it’s practical for some farmer to try to figure it all out would be doubtful.
John Deere loves to set everything up so you have to use their products.