Saw this implementation on a 2012 Winne Tour during our pre-purchase research. I remember thinking that is a very useful addition, yet simple (and inexpensive) for the builder to implement and provides an impression that the builder might really understand RV'ers and the RV lifestyle.
The Winnie cargo bay vacuum port was located passenger side about amidships as I recall - probably about the area where our water filters are located. Besides great for sucking dirt out the cargo bay, this location also makes it convenient to clean out the toad.
This should be an easy update given that the proper parts can be acquired. As another poster mentioned a "Y" fitting, some hose or pipe, a hose port w/door and an appropriate length of some light gauge 2 conductor wire (such as 22ga speaker wire) for the remote activation. Someday, when we get our coach back, we plan to make this additions so will report back with part info at that time.
Also check out my blog post here
for another inexpensive addition to this vacuum that makes it even more convenient to use - at least we think so. Unfortunately the exact device model described in the posting is probably no longer available but if you Google the part# or SKU you will find some similar devices.