Does the Oneida AXD000009 Ultimate Dust Deputy work on the FESTOOL MIDI Vac?

Yes, it is compatible with all Festool Dust Extractor models.The UDD has the same footprint and fits onto the various models of Festool vacuums the same way the Systainer tool boxes do, because of that, on the Mini and Midi, the UDD will protrude beyond their perimeters like the Systainer does.