The data sharing between the CRA and Elections Canada is optional, but if you want to vote, you've got to be registered - whether via the CRA or otherwise.

> but if you want to vote, you've got to be registered - whether via the CRA or otherwise

Technically true, but you can register at the polling booth on the day of the election, and there's a checkbox that lets you opt out of saving your data in the database. [0]

[0]: https://news.ycombinator.com/item?id=48015977

Being on the electors list is optional, is something you can opt-in to (and opt-out of), and is not required in order to vote in Alberta.

There are many reasons an individual may choose to not be on the list (eg. domestic abuse situations).