According to the Lansing State Journal article:
Bill Reed, president of UAW Local 602, which represents the hourly workers at the plant, said the layoffs were expected.
"This was a major vehicle change," he said. "It was kind of expected this was going to happen. I believe it's going to be for a short time."
Reed said the union has been advocating for a third product to replace the Acadia. Analysts predict that the plant could make a Cadillac crossover.
"I know (GM) wants to utilize the plant at full capacity," he said.
And here's an MLive article. as well.