Hi
It sounds like you can only link basic task data between different projects. My only suggestion in order to help you is to repeat the tasks in your project that are being handled by the other project and manually update them when you have progress reported from your colleagues. You could also change the colour of these tasks to another colour so as to make it clear that these tasks are being handled by another project.
If Kimberley sees your post she may have other suggestions.
Good luck.
Tony(OTPM)