My understanding is that when Elections Alberta shares the voter list with legit users (ie: sitting members of the legislature), it includes unique fictitious entries in the data. That way if there is a leak of the data, they can trace the source of the leak. Which they apparently have done.

I guess it's a form of a canary trap.

It reminds me of mapmakers including fake towns or other features in their maps, in case someone leaked them.

It's mentioned explicitly in the article:

"Elections Alberta salts the electors’ lists with the names of fake voters, so if one copy of a list is leaked, the agency can trace its origins. An analysis determined the list came from the Republican Party of Alberta, headed by Cam Davies, who, like Parker, has a well-documented history in Alberta as a political operative who pushes boundaries."

" reminds me of mapmakers including fake towns or other features in their maps, in case someone leaked them."

Sounds the same to me, but are you sure they are doing it like this, or you guess?