I hesitate to answer yes because we all know what is clear to us, is just an interpretation away from a change by the company.

Saying that, it's been my experience, under the old contract (and not much changed in that section with this contract) that all one needs is one positive minute to take vacation. Once you can take vacation, you can do anything permitted regardless of deficit. Many people purposefully go into deficit to use "super seniority" for the MUV window to get better trips. But, if you come up on a vacation period with a negative amount of vacation left, you can't take vacation.