Wouldn’t demolishing Boston City Hall be as difficult as the current demolition of the Government Center Garage up the block?
The two share similarities how they both sit atop of the subway line tunnels. In the case of Boston City Hall, the Green, Orange, and Blue lines sit underneath the building. Regular full scale closures of the Green, Orange, and Blue Lines would be necessary for the demolition of Boston City Hall. For the case of the Green Line, a closure from North Station to Park Street would be necessary due to the Government Center Loop sitting underneath City Hall.
Both buildings occupy decently sized footprints and seem to have similar heights. Boston City Hall doesn’t sit overhead of a roadway, so at least there’s that, but I think they’d still need to close some of Congress St., to demolish it. They appear to have similar architecture so demolishing the two might be identically difficult.