IMO undercarriage rust isn't really an issue in Alberta unless you get 10+ years into ownership and even at that you aren't likely to run into serious issues. Most rust on new cars happen around wheel wells, where different body panels meet, and trunks/hatches/lower doors due to plugged drainage paths. Basic rustproofing most dealers offer where they just spray the undercarriage won't do anything to prevent that.
Anyone considering something like this really needs to evaluate their typical length of ownership of vehicles. If you get a new car every five years or less it's a waste of money. If you keep all or most of your vehicles past 5 years then it may be worth it to investigate your options.
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