Seniority a thorny issue when employees transfer

If collective agreement doesn’t address seniority, consult past practice: HR expert
By Sheldon Gordon
|Canadian Labour Reporter|Last Updated: 02/04/2013

After Air Canada acquired Canadian Airlines in 2000, integration of the seniority rights of the two groups of unionized pilots was settled by arbitration. The former Canadian Airlines pilots complained they lost an average of nine years of seniority each, leaving them lower on the list than Air Canada pilots who had fewer years of service.

Seniority determines which planes the pilots fly, the amount they’re paid, vacation entitlement and pensions. The bitterness of the 1,200 former Canadian Airlines pilots who joined Air Canada lasted for years.

If, within a single company, workers from a non-unionized workplace were transferred into a unionized one and the seniority issue had to be addressed, what would happen?