There was a report of it in Anaheim at Cafe Casse Croute which features French Canadian food. Reliably it is featured at the Canadian Cafe in Monrovia and has been reported to be available and good at Dusty's in Silverlake (the last two unfortunately not in OC or LB - and don't recall ever seeing a report of it in LB previously).
Cafe Casse Croute
656 S Brookhurst St
Anaheim, CA 92804
My understanding of poutine is that its fries, gravy and cheese curds(gotta be squeaky), but can also be anything on fries even spaghetti sauce instead of gravy. I've been eating "wet fries" at The Hat before I even heard of poutine. The Hat has a location in Lake Forest...maybe you can ask for "wet fries" and try and find some cheese curds to add or ask them to add cheese(like they serve on their chili fries).
From the L.A. board I've heard Canadian Cafe in Monrovia is known for their poutine.