Because of the v-vents on the cups, I don't expect them to isolate too well. This was the case with the M80's and LP2's.
But keep in mind, they are not open headphones, so they still do isolate quite a bit, just not quite as much as a proper sealed headphone. The HD-25-ii is an example of a fully sealed on ear headphone.
The M-100 may offer better isolation based on circumaural cups compared to supra-aural for the HD-25ii.