The agency that operates GO Transit says demonstrators gathered around 7:20 a.m. today and restricted access to the Union Station bus terminal.
Spokeswoman Fannie Sunshine says the protesters have since left, but the modified service — which includes alternate boarding locations and connecting bus routes to train lines — remain in place for the time being.
She says customers can also expect delays at the Port Credit station and the Highway 407 bus terminal due to protests there.
Sunshine says additional staff are available to help customers during the disruption.
Metrolinx says it continues to monitor a strike by Union Station electrical workers employed by Toronto Terminal Railways, which has prompted recurring protests for more than a week.
Ninety-five workers with the International Brotherhood of Electrical Workers went on strike on April 20 and started on-and-off demonstrations in the days that followed.
The striking employees are signals and communication workers as well as train movement directors, and have been without a contract since December 2019.