Is it a good idea in the IT, software development\ consultation domain to team up with other freelancers to improve the quality and turnaround times of the project and give the clients benefits of a global team , Is there an existing model for this or a freelancers group which coordinates this?
I have always worked this way (with the exception of technical writing gigs). In general teaming up with other freelancers makes it possible to deliver greater guarantees than you can by yourself, and it makes it possible to tackle larger projects as well. There are some difficulties in working with new people (making work styles gel, ensuring you send eachother work that is appropriate to your expertise, etc) but these can be managed.
Now there are many times when this is not appropriate. I cannot imagine technical writing being a good case for this sort of team work because often clients want specific writers, but for more functional tools, it is generally a good thing.
There are two other points I would make in terms of IT services and software:
I have found that many customers have had bad experiences with loners, and that loners are harder to replace than team players. This makes being a loner a possible red flag for a customer. If you want to work alone you should be aware of this and at least have partnerships where you can hand off projects.
One of the very good things about teaming up is that if one team member takes on something that turns out to be outside his or her expertise, it may be possible to salvage the situation by handing it off to someone else. This is far harder to do working alone.