I don't know if they sought the location or stumbled upon it but after looking at Westside's website, it looks like a match made in heaven! Could develop into a true synergistic relationship!
My guess would be to save a few $$ on the booth. We're in the communications area and we do it at our trade shows also. We team up with a vender that can provide a benefit to our product and ours to theirs. That way you get more foot traffic to your booth most of the time. Looks like West Side is a pretty good one to team up with they have been in business since 1947 and their trucks deliver to multiple states right now.