In terms of the power of the Prime Minister to consult, I don't think there are any legal limitations on that; the Prime Minister can consult whoever he wishes before making decisions. I don't think it goes to the legal validity, in constitutional terms, of decisions that are made.
Concerning the broader issue of the impact of the Senate reference upon the interpretation of the amending formula in the Constitution Act of 1982, my view is that the Senate reference is still completely relevant to the interpretation of the amending formula. It's relevant in the sense that I don't see any reason to believe there was a decision to change the law in 1982 concerning the power of Parliament unilaterally to change the Senate. That power was there under section 91. Section 91 was turned into section 44. I don't believe there was any intention to change the law concerning the unilateral power of Parliament.
That being said, whether this particular reform is changing the fundamental features of the Senate is a very difficult question, and I think the answer would be different depending on whether the tenure of senators were renewable or not, and depending on how many years you're looking at. The relevant criterion under the Senate reference—and I think it's still relevant—is whether it's housekeeping on the one hand or fundamental features on the other hand.
It's not easy to answer that question, and the number of years I think is particularly important, as is the renewable character of the term for senators.