Does you company have anything like a central repository such as Plumtree or Peoplesoft? That is how we manage documents. We use to have a central shared folder on a global server to perform this function, but it did not have the check-out, check-in capabilities. What about something like TestDirector or a CM tool?
Success is the ability to go from one failure to another with no loss of enthusiasm.
~ Winston Churchill ~
Just Curious...What is in your test plan ? (is it a test plan or a test case document)
Why do folks need to update it concurrently ? I thought a single person (or maybe two) is responsible to update the plan.
I view a test plan as a respository of information, not a document. It should be continually updated, even during testing, to ensure that it is relevant. This should however be done in a structured manner with the right people updating the relevant information.
The most effective way to do this is to move away from using MS word and the like ( or spread sheets) and adopt products like Test Director.