Last edit: 15:30, 13 August 2015
I happened to come across this discussion and just had to butt in. In Russian, [sʲ] and [ɕ] are two entirely different sounds, as demonstrated by the minimal pair ще́ли (ščéli, “cracks, fissures”) [ˈɕelʲɪ] and се́ли (séli, “sat down (pl.)”) [ˈsʲelʲɪ].
My understanding is that [ɕ] is effectively synonymous with [ʃʲ]; no language contrasts them, and it isn't even clear what the putative difference between them could be.
That sounds about right. I've never seen it described like that though, I've only seen [ɕ] described as [ʂʲ], but [ʃʲ] makes a lot more sense.