Parametric Technology Corporation - PTC http://www.ptc.com
3D Mechanical Design Automation and Product Data Management Solutions
They use Tcl/TK to configure portions of Windchill, their enterprise level data management and process/workflow application.
They also use Tcl/TK to configure and administer Pro/INTRALINK, their Product Data Management solution for Pro/ENGINEER -their 3D Mechanical Design/Automation Product.
Tcl/TK has been used actively for several years, but it is not disclosed or marketed by PTC.