A shopping center near my house has an MXLV system (installed in the mid-to-late 1990s) which can be heard in https://www.youtube.com/watch?v=4SLVqFEkDOk this video. The slow whoop tone from the Wilderness Lodge video is almost identical to the tone used at this shopping center, albeit slightly raspier. This leads me to believe that it could indeed be an MXLV, as Steven suggested.
On a semi-related note, it appears that Cerberus Pyrotronics also rebranded voice evac products that were initially manufactured by a Montreal-based company named Electro Vox. I recall reading that Pyrotronics acquired Electro Vox (or Electro Vox’s line of fire alarm products) in the late 1980s, although I have doubts regarding the reliability of this information.
I unfortunately have little information about these Electro Vox/Pyrotronics voice evac systems. Modules from these systems Cerberus Pyrotronics Electro Vox H 436 Module Board 6153602 Fire Alarm | eBay show up on eBay from time to time.
Here’s a grainy photo showing a System 3 paired with what appears to be one of these rebranded Electro Vox voice evac systems. The voice evac setup shown in the picture contains a Imgur: The magic of the Internet VM-310 speaker selection module, a Imgur: The magic of the Internet VM-301 microphone and a Imgur: The magic of the Internet VA-330A trouble module (I believe these are the correct model numbers, but I’m not 100% sure; the three photos and information regarding the model numbers are from past eBay auctions).
The picture shown above is not mine, as evidenced by the watermark in the lower left corner. It was originally posted on the urban exploration website https://www.uer.ca/ UER, but I’m unable to find the original source.