This question was emailed to me and I did not quite have a response, so I contacted Alberta Education and here is the response:

Question:

I have been teaching this new Math 30-2 and have appreciated all of the information that has been shared on the arpdc site.  Especially the errors in keys etc... I have been behind in this course from early on and am finally working on the sinusodial functions chapter.  I thought it would be very similar to the applied 30 unit so I was surprised when I found the textbook using the equation y=a sin (bx - c) +d instead of what is on alberta ed's diploma formula sheet and what I have used in the past which is y= a sin (bx +c) +d.  Any idea of why the difference?  Did you find this created any confusion for your students?  Did you address the difference in your teaching?
 

Answer from Alberta Education

The format y = a sin(bx + c )+ d that was referenced throughout Applied Math 30 and the associated resources is, of course, mathematically valid. It became prevalent in that course because the TI-83/84 family of graphing calculators employ that format for sinusoidal regression calculations.

As the resources supporting the new Mathematics Program of Studies were developed in cooperation with the WNCP and resource publishers, it was collectively decided that the new resources would not, either explicitly or implicitly, promote one particular brand or type of technology at the expense or exclusion of others. There was also consideration given to supporting students who wish to upgrade directly from Math 30-2 to Math 30-1, which the new Program of Studies permits.

The alternative sinusoidal equation formaty = a sin(bx - c )+ d was chosen because it is mathematically valid, it is more similar to the general sinusoidal equation used in Math 30-1, and because it does not imply the most common technology or software is preferable to or better than others.

Teachers teaching the course will have to address with their students the fact that slightly different formats of a general sinusoidal equation may be encountered depending on the resource or technology used and that both versions are equally valid and correct.