http://www.truecondos.com/5-things-to-know-about-occupancy-fees/
I believe we will find out our occupancy fees around August or so. According to the above site, occupany fees are roughly equivalent to interest payments on the amount you still owe to the builder (i.e. purchase price - deposits, which means if you were buying this cash and weren't going to make monthly mortgage payments, you'd still have to pay this fee). I don't know if interest rates would be based on prime (3%) or the going mortgage rates or the rates for a loan...? It MAY be hidden away somewhere in some of the thick condo documents but I don't have them on me atm so I can't verify.
Regardless, no, you cannot NOT pay the occupancy fee. There's no way around it. From my understanding, the building can't get "condominium status" until x% of the building is occupied (I've heard it must be 80% occupied, others say 100% occupied before the builder can apply for condo status. Either way, the higher up you are, the shorter your occupancy period). You can't own something that doesn't officially exist, and the building does not until it gets condo status.
I'd suggest getting your pre-approvals in place now because if something changes financially later, that may impact your approvals (e.g. if you currently have a roommate paying you rent, that could count towards your income now). It doesn't hurt to lock in rates now because you're not bound to any rate or lender until you sign. It's just a safe guard to lock in their high rates now in the very unlikely event that interest rates sky rocket in the near future. At this point, with neither occupany or final closing confirmed, I'd say get your pre-approvals from different lenders now (and take any locked in rates they can give if possible - some can lock in for longer, others can't) and make sure you've got enough saved up for your last 5% deposit, closing fees, land transfer taxes (we'll have to pay 2 - Ontario AND Toronto tax!) etc.
Hope this helps!