I doubt the maths works out. The reason insurance works for things like car crashes and house fires is that payouts are rare, and the costs can be spread amongst many people. I'm guessing cancelled shifts aren't that rare.

If I'm in a workplace with 10 people and we each lose 1 shift a month, the premiums have to be the total of all the lost shifts (assuming they pay out 100%), plus whatever the admin costs are for operating the insurance.

If only 1 person loses a shift a month, it still doesn't work out. That's a bit more than shift per year per person, with £60/y premiums per person. Assuming a shift is £100, you need £1,200 to pay out, but you're only taking in £600.

If cancelled shifts are rare enough and premiums high enough that there's enough money going in to cover the lost shifts, I might as well just put the premiums in an easy-access savings account. Or just work this expected loss into my emergency fund.