There is action in Calgary on 127.775 with Edmonton Centre giving altitudes to planes landing into Calgary, departing Calgary and right now a Med flight going into Medicine Hat. 133.3 was listed as Banff Sector and has been changed. They are also giving flight clearances to a plane heading to Edmonton just NE of Calgary. I haven't looked for a map showing air sectors for Alberta but 133.3 seemed to control all traffic from being handed off over the Rockies, over Montana/Alberta border as well as Sask. Alberta border.
If this was at night, Centre will often link up transmitters so that one controller can work multiple areas when the workload gets slower. Haven’t been south for awhile, but from what I remember, aircraft from over the Rockies will make initial contact with the high altitude controller, and should they require further descent, typically into Calgary, they will be told to contact Edmonton Centre on the low altitude frequency. I believe the cutoff level is FL280 between high and low for most sectors I’ve listened to.
As for the transmitters, they are called PAL sites. Used when the distances are too great between aircraft and controller. Like I said before, they can be linked up by Centre depending on workload. The pilots will talk on the frequency closest to them that is assigned and that can also be rebroadcast on other frequencies.
For example, a pilot on a high altitude frequency that has been combined in northeast Alberta could be heard by a scanner listener in southern Alberta when the PALs are linked at night with perfect reception should the scanner listener be close enough to a PAL.
Not sure why this frequency change hasn’t been put in the Canada Flight Supplement yet, but might make its way there next publication cycle should it be a permanent change.
Hope that answers some questions.