Actually, there is no limit on the transitional rebate (the one that goes from 7 to 6, 7 to 5, or 6 to 5 depending on when you signed your contract.) The GST drop is across the board.
The $450,000 limit in the link troutman posted relates to the principal residence rebate that has been in place for years and the newer rental property rebate.
(If the home is less than $350,000 the rebate is 36% of the GST paid, ( be it 7, 6, or, 5%) If it is over $450,000, the rebate is 0. If the purchase price is between $350K and $450K the rebate goes down on a sliding scale from 36% to 0%.)
Again the transitional rebate applies no matter what the purchase price, even if you're not using the property as a residence. The only thing that is confusing about the transitional rebate, (other than the question of why the feds didn't just tell builders to collect based on the rate at the time of payment rather than the rate at the time of signing the contract, which would have saved all these headaches for everyone) is that if you do get the '36%' rebate in some form, it does affect the calculation of the transitional rebate because the '36%' rebate is calculated based on the rate paid as well.
If all you are worried about is the transitional rebate (i.e 7% to 5% or 6% to 5%...) here is the link
http://www.cra-arc.gc.ca/E/pbg/gf/gst193/gst193-08e.pdf
As far as timelines, most of my clients tell me it's about six weeks, although when one client actually called CRA to ask she was told around six months. (She got the rebate cheque in the mail a couple of weeks later.) I am advising clients 6 to 8 weeks on average, but no guarantees since it is the federal government you're trying to get money out of.