Upload & Sell: Off
I'm no lawyer, but I can't imagine that it would be retroactive in any way. Prior to the amendments, the only way to ensure you held the copyright to commissioned photos was to have an agreement in place that clearly stated you retained the copyright.
Here is the official transitional provisions:
Section 13(2) was the old section that gave copyright to the person who paid for the photos if there wasn't an agreement in place stating who owned the copyrights.
"60. Subsection 13(2) of the Copyright Act, as it read immediately before the coming into force of section 7, continues to apply with respect to any engraving, photograph or portrait the plate or original of which was commissioned before the coming into force of that section 7."
So in other words - arossphoto is correct.