Generally, you are correct. In this specific case several windows had to be broken outGenerally, the windows don't need to be broken. The rubber gasket holding the glass in place is removable from the inside or outside to allow removal of the entire plate of glass. The glass itself would be very difficult to break/shatter.
First, the Scouts secured passengers who seemed like they might have spinal cord injuries, his father told The Post. Then, they started popping out the train car’s emergency windows. When some became stuck, the Scouts used their shirts for protection and broke the glass. They evacuated everyone they could.