It was a regular plan for a year or so and then they said they were removing it soon and then there was a bit of an uprising and then they extended the removal and then they removed it.
@Dkloo2 Bottom line the $10 plan is currently not available.
At times it was a limited time offer, at times it was a regular plan offer but as of today July 28, 2020 Public Mobile does not offer a $10 plan. To see a full list of plans that Public Mobile currently offers please refer to https://www.publicmobile.ca/en/on/plans.
Hope this helps.