Unix (all flavours) and Microsoft

As the Linux/Unix profile in major organisations appears to be growing (or perhaps IT staff are admitting to using it now it's not seen as a stigma) are organisations cross training Microsoft support staff enabling them to support Linux/Unix systems? Or, are they using management software of some type? Or, are they hiring specialist Linux/Unix support staff and without creating resource pools and technology boundaries.

In the case of the latter, if the Linux/Unix team is 1 person who do organisations cope with holidays and sickness cover?