I think it depends on the type of cage, how you want to do it. Say you have a cage made by Ferplast that has a tube hole but it fits only Ferplast tubes. You can have a Ferplast tube coming out of the cage, then using packaging tape, make a join between a ferplast tube and an Ovo tube which could then be used to attach to the Ovo Loft.
Or say you have a hole cut into the mesh top of a bin cage, you could feed the Ovo tubes through quite a ways into the cage directly through that mesh so there would be no need to tape from the outside. They key with any join like that is just to make sure there is no room for the ham to squeeze through and that the join can't be broken just by the hamster digging at it.
I think adding it to another cage is a great way to use the Ovo stuff - since it's annoying for you to clean it as an entire cage, it would give you some flexibility without all the work.