mtv is not a commercial tool, and is tested only on simulators that I have access to (these are currently Mentor Questa/ModelSim, Aldec Riviera-PRO, Icarus 10/11, and Vivado). The compiler build is tested by running a large number of Maia programs, which produce a wide range of Verilog output. These simulators produce the correct results for all these tests, albeit with a range of minor differences (in output formatting, UTF-8 support, and so on).
The big holes in this list are, of course, VCS and Incisive. If you have spare licence time, and you need support, please get in touch.