Well, the services stopped when Alberta's population was much smaller. I think it may have doubled since then, with most of the growth in Edmonton, Calgary and the corridor in between.
The intercity and corridor traffic has increased considerably to the point that the existing road network will not be able to handle it sometime in the future.
So, then something will have to be done either a lot of money spent on roads, or something else. I imagine any significant new intercity rail initiative in Alberta would involve making a separate line for passenger vs. freight.