It's private property. You will be trespassing. They will probably bring you to a room at the base and have you sign a form stating that you will never step foot on their property again, in return for them not pressing charges.
Maybe it won't be that bad.... but I've asked similar questions in the past and not received a warm reception. Definitely call ahead and I think you will find that they tell you in very clear language that it is not allowed. If I remember correctly; even if you buy a downhill bike pass, there are very clear signs saying that you are not allowed on the service road (with a few exceptions where the road is the trail.)
In general, I don't think we do a great job (as self-propelled recreation folks,) at negotiating with the government to be able to access/cross-through some of these private areas in return for them getting their environmental/operating certificates.
It is frustrating that bikes continue to be banned from most of Garibaldi Park but Whistler is allowed to run a for-profit bike trail in the alpine at the top of the mountain and heli-skiing companies are allowed to access the park in the winter. It's hard to reconcile all those facts.
There is a big LNG plant being planned in Squamish. When it was a pulp mill, you could just take the ferry across, check-in at the first aid station and then proceed to hike up the surrounding mountains. It is unclear if anything like that is being contemplated right now or if we will be banned from crossing that property.