Benefits to which City primarily?Reading through St Albert's plan for the LRT, a two things are very clear:
1 ) It does interest them to connect with Edmonton via rail. Mostly, because it will lower their long-term maintenance cost for transportation infrastructure AND because it has the potential to make the city even more attractive for newcomers and migrants (it is delineated in their study), increasing tax base and fomenting developments in the area.
2) They have the cash flow to fund their 5 or 6 stops side of the line, connecting to Edmonton's Metro Line. St. Alberta has the financial firepower equivalent of a city 3x larger. Their plan is to start construction when Edmonton starts the last leg of the Metro Line expansion, so that they'll finish it 1-2 years after the LRT gets done.
Honestly, I believe this new position of prioritizing the south expansion is stupid and, considering St Albert's disposition to extend the line into their boundaries, looking NW is a much safer bet and would yield much more benefits in both the short and long terms.
Edmonton's LRT plan correlates with the City Plan, which looks at Edmonton proper first and foremost. I would hazard to guess that Edmonton looked at the demographics of each and chose to extend the existing south line further into City limits.
I don't disagree that extending to St. Albert has benefits, but who reaps all the benefits and how? St. Albert's population isn't huge whether they are willing to front the costs or not.