As of right now, even though the map shows those trails MTB riding is not allowed. That said, those trails aren't yet worth riding.
Several of us are working to get approvals to build the first shared (MTB) use trail. If you are interested in riding in Sterling why don't you PM me and I'll fill you in.
It's mostly fire roads and the single tracks have much hike-a-bike. If there was awesome single track, people would be riding it. The fire roads are useful if you're trying to connect RW to JH. Chris, I've found a way around the white water rapids water crossing since the time we almost drowned in it.
Not sure if bike accessibility has been 100% approved just yet but I can tell you that trail building has already commenced. This is going to be pretty significant for the MTB community in North Bergen and Orange County, NY.
There are trails. Lots and lots of fire road quad trails. Most hiking single track have unridable pieces. I wouldn't really call it fun unless you are a curious type or masochist.