My reading comprehension is a little low right now, but from what I can tell you have an Alberta registered vehicle that you want to transfer the ownership AND registration over to Manitoba? But because it is family, you are not "Selling" it, just "giving it back"?
The tax thing is true. Manitoba public insurance will charge you retail tax on the highest of the selling price or wholesale value. So even if you sell it to them for 1$ They will still charge you the tax on the wholesale value (only 7% I think, no PST)
I think ken is right though, your best bet is to go the "gifting route"
Car insurance in Manitoba is public, so most of the information you will need can be found on one website.
http://www.mpi.mb.ca/
Not the easiest to navigate, but should have the info you need.