In the context of G Major, is there anything special about a Am-Cm-Bm-Em progression?

Just from a chord progression there isn't enough to say this is in G major, but that's a different topic. The chords Am Bm Em are diatonic to some tonic and the Cm is "special" in that it cannot be part of a diatonic group with any of the other chords. In key G, three of them are diatonic - Am, Bm and Em.