WorldMark has a direct exchange agreement with certain Vacation Internationale locations. Similar to WorldMark, VI is a mostly western US timeshare system. I think the locations are available to book by any WorldMark owner but only as an Affiliate Rental, no special Pass is required; at $0.15 per credit, VI reservations are expensive by WorldMark standards.
The first building constructed at the Village at Steamboat was a VI location. Two additional WorldMark buildings were constructed on the site in the early 2000s, so the relationship goes back a few years.
It is interesting that the VI locations are included through Wyndham Club Pass. It really did open up the whole WorldMark system to Club Wyndham owners who can use it.