It says they're food grade. I would think they would be just fine for fermenting. It's just like a huge plastic bucket. Are you going to bump up to 40 gallon batches?
I think they would be fine. I think you can even get food grade liners that might make cleanup even easier. Or you can scale up Doc's carboy/keg cleaner to gargantuan proportions...
Mylo
"Life is too short to bottle homebrew." - Me
"HEINEKEN? Fuck that shit! Pabst Blue Ribbon!!!" - Dennis Hopper, in Blue Velvet