Legally speaking, they have a right to distribute copies. But Youtube isn't required to accept it though, and their copyright claim system is already somewhat notorious for the degree to which non-copyright owners to try to strike down videos for claimed copyright infringement.

Steamboat Willie is probably the single most famous work to fall into the public domain since Youtube started. It is (formerly) owned by one of the most famously aggressive company in protecting IP. Youtube itself is also owned by an entity that is on the other side of IP law than Disney, but definitely far less aggressive in pushing those claims.