It's not really ported. tkinter just builds a full Tcl interpreter as a Python extension and passes command strings over to it. This is the use case Tcl was designed for. You can get access to the underlying Tcl instance and issue non-Tk commands.
My next question to myself was what hardware was running Tcl in c.1997 Cisco equipment? What porting effort was required? I understand there was some proprietary feature work for Cisco IOS, but I don't know what architectural work was required.
Long term, the Cisco router support became the non-recursive execution engine (of Tcl 8.6) which stopped things from blowing up on the tiny stack sizes that Cisco equipment is configured with.
