How does it fail? It produces a movie but the background isn't transparent?
For what it is worth, all that command is doing is a regular export that sends along a little extra information to tell AME to select that particular preset. Maybe somehow your copy of AME is missing that preset or has been modified so that it isn't actually preserving the alpha channel?
If you do a regular export and change the settings so that AME renders a format that has an alpha channel it should work. This answer seemed to work (this predates the addition of the dedicated menu item):
Re: Can I export from Character animator in .mov with background transparency?
There's also this guide:
Depending on how big your scene is and what you're doing with it, you could also export to PNG + WAV and import that instead.