Obviously until one has the universal remote in one's hands, one doesn't know the exact answer to some questions. But if they work the same way 2.4 GHz digital spread spectrum R/C transmitters and receivers do (this is what LionChief and LionChief Plus are, technically), one binds the specific loco (or airplane) to the specific transmitter, and there is no interference even if someone is using the exact same airplane and transmitter nearby.
Thus, presumably, each loco will have it's own unique identity, just like R/C airplanes, cars and boats that use this technology. Indeed this current R/C technology is superior to the identity systems used with TMCC, Legacy and DCS for loco identification where specific numbers are used, not unique digital identities. Therefore if Lionel uses the same technology implementation that is used in R/C airplanes, there will never be any conflicts between locos in one person's handheld and another person's. At least when the multi-loco remote is in use.
For the remotes limited to a single loco this will not be true, as these seem to be permanently "bound" to that particular model of loco. For these, it will not be possible to independently control two identical locos with two identical original remotes in the same vicinity.
Exactly like any two Railking set locos with two of their infrared remotes . Indeed, no two MTH set locos can operate independently without DCS. Whereas two different LionChief set or Lion Chief Plus locos can be operated independently right out of the box, no additional equipment needed.
The two identical LionChief set locos should not be a limitation if there are multi-loco remotes available, which should deal with this issue. And the street price is about $40. You can have three or four of these around for the cost of one Legacy or DCS remote .
That said, obviously we need to wait and see what Lionel's implementation of this is. My guess is that if it's very popular, we'll see remotes capable of handling 5 or 10 locos, just like some R/C transmitters can. I think the Legacy to LionChief bridge is not impossible technically but there may not be enough of a market for it. But never say never.