Are there any issues with this or chances of controller crossover?

i can't speak on behalf of a P3S, but i have flown my P3A around varying types of Phantoms & others before without issue.

will have to wait for someone to chime in that has an S and has flown with other S'ers. ;)

can't see it being much different though.

I believe and please feel free anyone to correct  me if im wrong but when your bird was binded to your  r/c a digital handshake occurred thus your bird and controller will only respond to each other.Don't think there are any limitations other than reduced video if your both transmitting on the same hd channel which you just select manual and chose a different channel to your mate.Again I don't think it would matter being on the same hd transmission channel other than you would get more interference thus less range.

I have seen several Phantom 3's flying at the same time at the Dji Games videos, so probably it is okay.

I have flown next to another P3.  The RC signals were fine.  At first the video feed was very bad.  I landed it, changed the video channel, and everything was fine after that.

I was trying to fly with a friend of mine this weekend. She has a new PH3. I had severe video interference even though I had what appeared to be a full signal. I changed to manual and selected a clear channel and had the same results. Video loss at close range, severe stuttering or garbled video image. I tried again later that day when she went about 2000ft away to a friends to fly. I stayed put and launch mine without experiencing the issues. I even flew over to her location to within about 100 ft. She was not flying, but was powered up and on the ground. We didn't have time to play around and see if we can get to the bottom of the problem, but it was very bothersome. I wasn't expecting to see these issues.

Two can fly together no problem. I have flown my Phantom 3 with another forum member flying his, in the same air space.
We didn't encounter any problems or difficulties. Seems that more cloud fly in the same flight area without a hitch.

RedHotPoker