Permissions are project based at the moment, but there is some interest in changing this to work on an object level as well so it should be possible to do in the future.
yes, because I have a similar problem. For example I have lot of projects with different software developers and I have one system administrator for all sevrers. this mean that is not possible that members of other project to contact the sysadmin because he is not added as a member of each project. and i dont want to add him in all of that. the best solution will be to have the system administrator user that can be contacted by all project teams but where sysdamin can see only task and messages directed to him and not other team messages and tasks.
Please come and join us on the development mailing list if you are interested in contributing to or discussing this type of access right. There is currently a short description of the work to be done here:
http://wiki.clockingit.com/dev:access
Input is useful from various people to ensure that what is being developed meets all needs.
Mailing list here: http://lists.clockingit.com/mailman/listinfo/dev