I have just dug out my log book and I was in Calgary for the first time with L1011-500 G-BFCB on 5/11/81. Did a return flight due to vibration on #1 fan in G-BFCE on 7/11/81 and went Calgary-LHR on 8/11/81.
The routing for the Tri-Star was either LHR-Calgary-Vancouver or LHR-Edmonton-Vancouver. If it was outbound via Calgary it came back via Edmonton and vice versa.
I seem to have spent almost half of December 1981 shuttling between Calgary-Vancouver-Edmonton having left LHR on 15/12/81 and getting back on 27/12/81.
You are correct that the service was for only a short time and was operated with the -500 version of the L1011.
After April 1982 the service seems to have been changed as I have several trips from LHR-Seattle-Vancouver with some via Edmonton. The last of those trips for me was 16/9/82.
I hopes this helps a little.