I would agree with siping to get more traction in wet weather, but don't agree with regrooving. My brother the tire man definitely says you don't want to regroove on tires like we have for what we're doing. On trailer tires on semis they give you a few more miles, but they also produce some of the problems we've all seen on the side of the roads with tread separation. They make old tires look newer, but they're more likely to fail.
Siping does help in wet weather, but it has also produced a little shorter tire life, which may be imperceptible to most of us in motorhomes because we often run into an age issue first. The weight of our coaches does help with we weather, so the impacts of siping are probably less than with a lighter vehicle.
Former Owner, 2006 36MDDS
2010 Arctic Fox 22GK Travel Trailer
2007 Toyota Tundra