With the local judge appointed there, I don't think they have any chance of challenging the law because it seems that the Judge supports the law as mentionned in the article, so no chance that their case would even reach higher courts
That's the point of an appeal. You lose the case, but appeal because the judge made an error in law. That law would be the Charter.
Or you win the case, but the Crown appeals, also based on the judge making an error in law.
They probably have more than one judge in Cape Breton. So it's not at all certain that they will all be convicted.
But I think that the Crown will try everything to get a plea bargain on something like a reduced sentence or conditional discharge first. Failing that, they will likely drop the charges after dragging the case through cancellations and rescheduling. They will do that because if they lose the case based on Charter rights, the law could be quashed altogether. The Crown doesn't want to risk that, since we'd be back to square one with no prostitution law on the books.
The paper just won't give up listing the names and addresses of the accused. I wonder if they face a defamation suit if some are acquitted.