To expand on Mike's answer a little: The technology used for these long range Bluetooth headsets is proprietary so one manufacturers headset can't communicate with another's. If they agreed on a standard I reckon that the uptake would be greater rather than trying to make it so that riders in a group have to all buy the same brand. Maybe it's more complex than purely being a marketing strategy
You may find that intercoms integrated into helmets such as BMW maybe compatible with one other brand due to the intercom actually being sourced from them. You'd need to research that one and make sure before buying though.
Might not be a consideration for you but if you ride as part of a larger group the maximum group size of a comms group can be an issue. The BT systems limit this to as low as three or four riders with the earlier systems. later systems have more but still not many.
