They definitely have no problem sending up pups when they are planted 1 foot beneath soil level. I have 2 plantings from last year, and they've been pupping like crazy this year. If you can get them even deeper, it may be even better as long as you back fill it in with lighter materials like peat moss, mulch and anything but clay soil.
The only problem with having it planted so deep is that it's very hard whenever I dig for pups because I have to go all the way down to get them.
Here's the thread that shows their progress
Musa basjoo growth after 2 seasons