I want to try to get a group playing this and before we pay to try out. Can Demo users play online? If so, is it only with other demo people? We really want to try the cops mode.

Yep just unlock demo and u free to play Blackwood GP Historic and Rallyx in XFG XRG or FBM.

Quote from Jerry Cherry pie :

If so, is it only with other demo people?

no, licensed people can also join