You certainly can take public transport to any game in Chicago. But it doesn't mean it is easy or convenient at least in my mind. Getting to a Cubs game via public transport is not too bad. But leaving in the masses sucks.
Our little trick leaving Wrigley Field was to walk a few blocks north to the Irving Park/Sheridan train stop, get on going southbound, and enjoy our choice of seats while the train pulls up to the masses at Addison.