Yes indeed. (Apologies off topic to your question Roversfan2001) Several years ago, myself and three members of my family travelled from Preston to Carlisle using the route "Any Permitted" SORs, on a diverted Super Voyager service over the Settle and Carlisle route.
Luckily the train started at Preston, so we were able to very easily nab one of the two tables for four in coach E, despite not being able to reserve seats. We had a few hours in Carlisle before getting the same Super Voyager back to Preston.
It was a lot cheaper than buying CDRs route via Penrith (which would have been valid because of the diversion) and paying £15 each. We had no trouble with Train Managers wanting to charge us the upgrades. The only minor issue on the way back, was the CSA in the shop wanting to charge us for the tea/coffee, being unaware of the free upgrade policy, but she phoned the TM and all was well.
I once got asked for my ticket by a CSA upon leaving Carlisle (again a few years ago), on a diverted service to Preston, via Settle. It was a double Super Voyager. I sat in the front set in First Class, with a Standard anytime ticket on a Sunday afternoon. I was asked to leave First Class, which I refused to, as I had a valid ticket/it wasn't full. There was only one Train Manager on the train, who was in the rear set, so the CSA got in touch with them and the TM confirmed I was perfectly ok to be in First Class.
I've never had my ticket checked by a CSA before and it was also unusual to have at seat service on a Super Voyager train (in my experience but I know it does happen) on a Sunday. I questioned how I could upgrade using Weekend First, had I been holding a Standard Off Peak/Advance ticket, as the CSA didn't have the means to take payment for it.