The union announced Tuesday it planned to finalize the move with the Ontario Labour Relations Board by week's end.
But the union needs approval from 40 per cent of the plant's employees before a vote can be held. Toyota is challenging that the support exists.
If the vote goes ahead, Toyota spokespeople said the company would ask for the ballots to be sealed while they determine if over 40 per cent of the workers signed union cards.
There have been some new employees hired in the last few weeks and numbers are getting blurred.
Toyota spokespeople said there are over 3,000 employees at the plant while the CAW said there is only 2,000 production and maintenance staff that would be part of the union.
The CAW has been trying to unionize the plant for years as memberships dropped due to layoffs and employees at Honda Motor Co. Ltd. and Nissan Motor Co. Ltd. rejected their attempts to unionize.
Toyota spokespeople believe a union is unnecessary and see the CAW's interest is purely for the $2 million that would be raised in union dues.
But the CAW responded that the union has a strike fund of $60 million and is financially healthy.