In the silicon industry it’s definitely tcl only. Zero Lua. But every tcl script I have seen is extremely simple, often just a bunch of commands to the EDA tool that reads like a list of bash commands.
Tcl scripting gets more interesting when you want to talk to a design running in an FPGA over JTAG. I have a toy CPU project which I've so far tested on Altera/Intel, Xilinx and Lattice FPGAs, and a debug interface where a C-based ncurses debugger connects over TCP/IP to a Tcl bridge which talks to the appropriate JTAG interface for the particular type of chip.
I'm also a big fan of the full-fat Tk-capable Tcl in Altera's SignalTap / Virtual JTAG - I used it recently to plot histograms on-demand for profiling RAM / Cache accesses.
