To hopefully add clarity to your situation, some text from the Flight Operations Manual which describes the Flightdeck Jumpseat boarding categories and priorities at US Airways:
9.3 Boarding Categories
The two boarding categories are space positive and space available and within each are sub-categories. Both categories and sub-categories have their own priority system.
• Note •
Boarding categories apply to mainline operations only.
When riding on Express or affiliates, their jumpseat policies apply.
9.3.1 Priority System.
Space positive has priority over space available.
Within each category, sub-category 1 has priority over sub-category 2, subcategory 3, etc. The captain may alter the priority order if circumstances warrant.
As two pilots from the non-wholly-owned express carriers, you would both fall into the space available boarding category. You would also both be in subcategory S4 of priority for the flightdeck jumpseat. For the majority of the priority subcategories, the tie-breaker then goes to whomever has the earlier check in time.
You might notice on the Jumpseat Travel Request form that there is a location for the gate agent to record your time of check-in, but there is no where on the form to list your date of hire. That is because we use time of check-in for most of the jumpseat priority subcategories, DOH only comes into play when non-reving for a seat in the back.
If you had some time, and a gate agent willing to hear your plea, I think printed on the backside of the jumpseat request form there is also the computer file path for the agent to read the "FAQ" and how to handle the flightdeck jumpseat request and boarding process.