Early Rocky Mountain Road frame.

From what I understand Vitus had arrangements with many bike manufacturers Peugeot, Motobacane, Mercier, French-Loire, Gitane, Bertin, Cilo, Bertoni, and a bunch of others.

Here's a decent resource if you're interested. https://on-the-drops.blogspot.com/2016/12/the-peugeot-px-10du-vitus-979.html?m=1

I'd have to assume that there would have had to have been some sort of licensing agreement, especially because they were co-branded.

I'm located in southern Alberta, I picked this one up out of Calgary.
maybe they had a commercial arrangement with RM?
This is the most logical explanation. Vitus would have benefitted from RM's Canada-wide distribution network for their product. Putting the RM decals on the HT & ST was likely part of the distribution aggreement. While one of the above links had RM on the downtube you'll see the others only limit it to the HT & ST decals. My own recollections at my LBS also match - just HT & ST decals.