I have been having a long discussion with FrSky around this.
First off all I have been assured that the Telemetry units have Unique GUID's which do not overlap with the V8 GUID's and they will never overlap with each other.
The V8 Units however run on a bit of a weird system.
The GUID are assigned by the sounds of it randomly at the factory in a certain range. Which is why they can not tell us how many share a GUID at this point. Then there is the channel mapping. The 2.4Ghz band has been divided up into 250 channels. Then FrSky will use 50 of those channels. Each unit has a random channel mapping routine at startup which is meant to ensure via a random type calculation that if there are two units with same GUID that they don't end up on the same channels.
However as the two guys here have found there is a bit of a flaw in that as it seems it can overlap.
Seeing this is the first occurrence of this happening FrSky have rightly so requested the units back for analysis to see how big a problem this is esspecially seeing this has been the only recorded case of it happening. If someone else has had this happen to them I would like to hear about it and I am sure FrSky would as well. It may well be that there is something else causing the conflict and there random logic routines are in fact sound. However in theory the GUID sounds the most plausible, so FrSky correctly so want to work with solid evidence rather than working on assumptions. However are not closed to the fact that the GUID most likely is an issue and are in the background looking at ways to correct it if it is proven to be the case. Firmware flash updates or something along those lines may be part of the solution or there may be an easier way they are looking at it.
Unfortunately I am still waiting the one unit to be returned to me so I can package them up and send them to FrSky.
I also asked FrSky about the possibility of them building a unit to detect the GUID's for conflicts at the field. Which in turn can be used to get the units re-flashed with a new GUID. They have indicated that they are looking into that possibility and are best trying to figure out a way to reset GUID's without causing further conflict.
However a lot rests on these two units being analyzed. I have e-mail the user that still needs to send the other unit back however I have not had a response yet. Being the holiday period here in NZ I will e-mail again next week when the majority of people get back from leave to see where the other unit is.
I will let you know as soon as I have received the other unit in question and as soon as I get feedback from FrSky on the analysis I will let you know.
So in short if you want to be assured of a Unique GUID the Telemetry system is your friend.
Until then if there is a new FrSky user at your club double check your systems before flying. From the testing I did at the flying if they have not conflicted in the first 4 power on power off cycles then they are safe. The two units in question had a 3 in 5 chance roughly of taking each other out so it was a high chance and almost guaranteed. So if you have been flying with your buddies and never encountered this then you will be fine. It is the new units the the field you need to watch out for.