From NCPR, Canada, on May 24, 2023:

The evening of Mother’s Day a couple of weeks ago, the ferry that connects Wolfe Island with mainland Canada in Kingston went out of service due to a mechanical failure. The ferry didn’t run again until well past the beginning of the workday Monday morning.

The ferry’s been a point of frustration for more than a year now for the 1,400 people who live year-round on Wolfe Island, which is where Lake Ontario empties into the St. Lawrence River. The island population balloons to several thousand residents and tourists in the summer. The ferry serves almost a million passengers a year.

The old ferry, the Wolfe Islander III, has been out of service frequently with mechanical problems. Two new ferries aren’t in use yet.

A labor shortage is an additional complication, says Ferguson. “They’ve had to reply on temporary services to fill the crew ranks and there are times when the ferry just cannot go because they don’t have enough crew to staff it.”

Island residents have been stranded sometimes for hours, and the Coast Guard has had to step in to help with medical emergencies.

https://www.northcountrypublicradio.org/news/story/47862/20230524/wolfe-island-relies-on-its-ferry-to-kingston-but-the-ferry-has-been-less-than-reliable

Sounds a bit like Arran though with a shorter, easier, crossing. On Mothers’ Day 2023, 19 March, Calmac’s Arran service ran 9 sailings on time, 100% reliability, and across all of the 262 sailings in Scotland that day, CalMac had 100% reliability. The seasonal average was 95.4%.

Just one day, I know.

So, also in Canada, British Columbia (BC) Ferries operates a fleet of 41 vessels serving 47 locations on the coast. CalMac has 34 vessels serving 22 islands but with more than one terminal on the bigger ones.

How do they compare?

Well, daily data on reliability are posted for all of Calmac’s up to 500 sailings.

BC Ferries data do not seem to be so easy to access.

From CFTK-TV News in 2021:

Most notably, route reliability dropped to between 75-80 per cent for the Prince Rupert – Port Hardy ferry and between 90-95 per cent for the Prince Rupert – Haida Gwaii ferry during the first quarter of the 2022 fiscal year (April – June 2021). Both lines saw increases the following quarter.

https://www.cftktv.com/north-coast-regional-district-plans-to-send-letter-regarding-declining-service-reliability-on-northern-ferry-routes-1.5713747#:~:text=Most%20notably%2C%20route%20reliability%20dropped,saw%20increases%20the%20following%20quarter.

In the same season, Calmac had 95.4% reliability, up to 20% better than BC Ferries:

https://www.calmac.co.uk/calmac-performance-data-browser?date=31%2F05%2F2021

CalMac seems to be, on the above comparisons, at the very least if not more so, a reliable ferry operator.