The past 4 or 5 years have seen significant changes in the situation with respect to mobile phone coverage in Canada.
When we first started cruising in eastern Canadian waters in 2012, mobile phone coverage was extremely patchy outside of the metropolitan areas and getting a PAYG bundle for phone/mobile data was both difficult and expensive. Although at first sight a PAYG SIM card was a cheaper alternative to using a satellite phone, in practice we found the benefits were marginal, especially since a lack of coverage meant that we often had to use the satellite phone anyway.
Since then coverage has improved significantly and when cruising the Nova Scotia and Newfoundland Coasts, and the inner reaches of the St Lawrence River, it was rare not to have a good 3G/4G mobile phone signal when mooring or anchoring for the night, and often we had a good signal up to 5 or 6 miles offshore when cruising between harbours. Even the south coast of Newfoundland ,where the remote fishing settlements have no road access , has remarkably good coverage in relation to the small number of people living there. The only areas without any coverage whatsoever are the north Quebec shore of the outer St Lawrence River and Labrador.
At the same time prices have in general dropped and buying a Canadian PAYG Data and phone bundle now represents reasonable value for money and is much more convenient than relying on wifi hot spots. However the value for money aspect only extends to data usage and the making of local calls. Making and receiving international calls on a Canadian PAYG SIM card remain extremely expensive and for such calls you may find that a roaming international call made from your home mobile (or even satphone) works out cheaper.
Whilst coverage and prices have in general improved, unfortunately the same cannot be said of customer service levels. Pricing structures remain extremely complex and opaque, with all sorts of hidden charges waiting to catch you out the moment you stray outside of what may be included in your PAYG bundle.
Very few retailers, and even the mobile phone company call centres themselves, seem to understand exactly how these charges work and even a simple question like "How much will it cost per minute to receive an incoming call from overseas" is not readily answered - and when it is, you often get a different answer each time you ask the question!
Likewise, what should be simple administrative tasks like topping up your account balance and adding minutes/ data to your account can end up being inordinately difficult, with online top ups simply failing to work, instead requiring lengthy and frustrating calls to the customer help desk (all of which eat into your call allowance) .
The bottom line. If you are planning on cruising in Canadian waters for an extended period and need frequent telephone and mobile data access then it is probably worth enduring the hassle of getting a Canadian PAYG SIM card and keeping it topped up. However for shorter visits and/or only occasional use you may find that getting a roaming extension for your existing home mobile phone is not that much more expensive and avoids an awful lot of hassle.
If you do decide to get a Canadian SIM card then it pays to shop around as prices and what is offered in the various PAYG bundles, seem to vary greatly from year to year - and the best value provider one year may not be so the next year. However, when it comes to coverage in the maritime regions, Bell appears to have the edge over other providers, although the same cannot be said of their customer service which epitomises all that is bad about a call centre based service!