The L-1011s were incompatible with the rest of UA's fleet and I'm sure they never intended to keep them. As far as I know, they operated them in Pan Am's configuration, as I believe very little was done to 'Unitedize' them. Even at Delta these remained 10-across in coach (3-4-3) (a la Pan Am) as opposed to the 9 across (2-5-2) in other DL L1011-500s as as far as I know they were restricted to the Asian markets on the theory that more of them can be squeezed into the same space!
When these were with UA I recall that you could ride one from LAX or SFO to HNL, but as far as I know this was the only US domestic route with the UA L-1011.
Within Delta, which acquired five of them (as mentioned), these ships were known as PUDs (Pan Am United Delta). For the benefit of our non-US readers, 'pud' is slang for a certain strategic male body part. As far as I know DL parked their PUDs and the remaining -500s in their fleet are the ex-AC or ex-PA direct sales.