Usually we borrow equipment for review from manufacturers/distributors, but in case where they are unable or unwilling to supply we have been known to go out and buy products we feel justify such a course of action in the interests of the readership.
In an ideal world we would go out and buy every product we review, but a) this would have a huge impact on the cover price of the magazine, and b) it would preclude us from reviewing products as they appear in the shops, given the lead-time to which print magazines work.
Manufacturers have no knowledge of the outcome of reviews before the magazine is published - as EB Ricky showed the other day, subscribers usually see the magazine before the manufacturers -, but yes, we do get feedback(!) from companies when a review appears.