How to use for managing developments which span multiple projects? I MUST be missing something obvious as this is such a common situation with enterprise product development 
Ill try to explain the scenario Id like to handle:
For example, lets say I have "ProjA", "ProjB" and a new "FeatureX" (HOSLog support reporting by status type).
ProjA has 3 components: A1, A2, A3 and 2 Versions: 1.2 and 1.4 (i.e. Web UI, WebService, Database)
ProjB has 2 components: B1, B2 and 2 versions: 3.2 and 3.4 (i.e. TPC UI, Middleware)
What I want to do is enter a Card for "FeatureX" with to track dependancies existing among separate projects:
Subtask1: "A" which relates to ProjA, A3, 1.4 (Extend Web database to use reference table for storing HOSStatus data)
Subtask2: "B" which relates to ProjA, A2, 1.4 (Extend Web WebServices to use new HOSStatus table and add web methods for searching/sorting on status by date and driver/driverGroup)
Subtask3: "C" which relates to ProjA, A2, 1.4 (Extend Web WebServices to use new HOSStatus table and add web methods for searching/sorting on status by date and driver/driverGroup)
Subtask4: "D" which relates to ProjB, B2, 3.4 (Modify TPC Middleware to insert HOS Status into HOSStatus reference table instead of HOSLogs table)
Currently, I can easily add a new Card in ProjA with Subtasks 1,2,3. I can also add a separate card in ProjB with Subtask for #4 *BUT* I want to be able to group these two cards (subtasks?) under the same "Feature" development.
I attempted setting up a single global project then creating components for ProjA and ProjB but stopped when I realized that components cannot be versioned.
How are others accomplishing this?