from what I've heard, the RU side in Toulouse, and the city government are much more occomodating to RL then can be said for Perpignon (sp?)...
That said, I think that they could work out a ground share agreement for the existing 19,000 seater RU stadium.
Then if they have some very big matches and are able to fill a larger venue (say for the inter/french derby, play-offs...) they could make plans to book the soccer stadium which seats 37,000 and is a top notch venue. I've seen some RU matches from here...