is it possible we can install two different sccm servers one for workstations and other one to manage servers is it possible?

Yes, you can do that however, you should try to use ip range as boundaries so that we can avoid the issues like overlapping of boundaries.

we like server team to manage servers and workstation team to manage desktop only.

SCCM 2012 will be helpful to do these kind of segregation with out creating two diff hierarchies.

we like to have sccm setup in few weeks. do you know when cm2012 going to be release?

I don't know the exact dates. It will release by Q4 2011.

I like role-based security, but here's a twist to the original question:  Let's say there are separate workstation and server management teams.  They are so adamant about the separation of responsibility that they have created separate SCCM hierarchies:  One for workstations, and one for servers.  However they have joint administrative capacity/responsibility for one server in each branch office that hosts SCCM roles.  The workstation team is responsible for maintaining the SCCM roles of the server, and the server team is responsible for OS management, including patching.

So the SCCM-related servers in the branch offices need cross-hierarchy management.  They need to serve their purpose as part of the workstation hierarchy, but the OS needs to be managed by the server hierarchy.  I wonder if a server can host roles in one SCCM hierarchy while being managed by another?

Thanks...

I would never recommend doing this and it is most likely unsupported.

Do non-standard things, get non-standard results.