Likely only through the courts.
As someone who would very much like to own a recreational property in Canmore one day, I really hope the Town accepts the decision.
Adding capacity to Canmore is good, glad there appears to be light at the end of the tunnel for this Canmore project.
That said I hope small, popular, and physically constrained mountain towns get way more serious about growth planning within their existing boundaries too.
Canmore has missed many opportunities the past 3 decades about growing sustainably and more efficiently through intensification. Downtown Canmore still has loads of surface parking (of course 100% occupied and gridlocked because no amount of parking can realistically be built to serve demand), really low densities on all surrounding streets with houses and townhomes, and many of the easy development areas adjacent to the highway have been hit-or-miss - often reasonable density and mixes of uses, but mixed randomly with a mish-mash of car-oriented apartments and gas stations.
Compared to many towns, Canmore really tries hard on the transit, cycling and walking infrastructure and should be commended for it. But overall it's the land use that misses the mark creating a larger-than-necessary footprint town with crazy traffic and extreme levels of gentrification. There's practically no supply of apartments or affordable housing in the core of the town as a result, nor any real plan to get any volume of new units at any material scale.
In hindsight, a better approach would have been to really jack up the densities in the 1990s and 2000s boom eras in the core , and have had a far more holistic, aggressively dense urban plan for the highway adjacent strip for expansion that's now mostly filled out with a hodge-podge of inefficient uses. Also, far more attention should have been paid all along to getting a solid, high-quality transit/rail link to Calgary to remove as many vehicles as possible. This would have had two benefits - you still get all /more tourist dollars to power the local economy but at a lower cost as they don't need to have vehicles accommodated to visit. Secondly, better access from Calgary without a car reduces the pressures on parking that manifest itself in high parking minimums in the land use rules as well as in development community opposition talking points.
3 - 5 times the population would fit in the existing footprint if Canmore allowed 5 - 6 storeys everywhere and reduced car-orientation substantially over a few decades (although that ship has likely sailed as nearly all obsolete housing stock has been largely replaced recently with low density, ultra expensive housing). That would have been a real alternative if the town was so concerned about consuming more natural land for development, but they didn't take that route and therefore ended up with the mish-mash of ultra-unaffordable, urban/mountain town/highway adjacent sprawl pockets.
Mountain towns should learn they can be more than 2 or 3 storeys and still retain that mountain charm.