I just had a look at the RIV site, specifically the "Recall clearance" information. The page provides two drop downs, one for the "manufacturer" and the second for the "type" of RV. I looked in the type list and low and behold, trailer is included. That would mean to me that by implication, trailers are included in the recall cert requirement. I don't think I would want to be trying to import a "trailer" without the recall cert! If called out for no cert, you would then own a trailer that you could not bring into Canada and therefore you would be in the Seller's market in the US. There is an alternative I would guess. Employee an import broker that is experienced in the vehicle importation process however; that would have a serious impact on the "savings" gained by importing. I would further suggest that one acquire the recall cert BEFORE taking ownership/title to the vehicle. I would not assume that a rv broker/dealership knows the ins and outs of import to Canada. Due diligence here would include overseeing the whole process to avoid owning an RV that is not importable to Canada.
Exemption from the RIV requirements, including the recall certificate, are listed at the following web site. Please note that there is AN exemption for any RV that is older than 15 years. The remaining exemptions include a work vehicle, a temporary import and pre-clearance These exemptions are not likely to fly for an RV, I would suggest.
http://www.riv.ca/RIVExemptions.aspxVic