Not only is the plastic decking material expensive, it’s also very heavy, and is not a good insulator since it is high density plastic. It’s not a foam material. It doesn’t have millions of air pockets to act as insulation. I would sure hate to pick up a deep made out of the stuff.
Could you build a hive out of the stuff; probably. Is there better materials to use; definitely. Being in Canada I would build a polystyrene or polyurethane foam hive if you want an energy efficient hive. If you don’t care about energy efficiency, I would probably do what bee keepers have done for generations; use pine boards. There’s a reason beeks have used solid pine for so long; because it will hold up for many years in a bee hive. On a wood deck, the water will still on the horizontal deck boards and eventually rot them out. On a bee hive, most surfaces are vertical and not as much water sits on the wood to rot it.
In Michigan, they sell a lot of the high density plastic decking material too. Personally I hate the stuff for a deck, but many people love it here because it is maintenance free. No painting and staining. I think that is the bigger selling point for the product around here. A wood deck will last a long time in Michigan IF you keep it stained and sealed every few years. Solid wood really doesn’t rot that fast when protected with paint. I’ve got clapboards that are over 100 years old! Wood can outlast you :)