I asked the same question 3 years ago. Was told that the negotiator's notes showed:

Deadhead Deviation available in three ways. Travel to:

1) The pilot's base.

2) The pilot's home of record.

3) Anywhere in the contiguous 48 states.

Ability to deviate is good for up to two days before or after the scheduled deadhead. Positive space pass is available for multi-leg deviation, even if one of the legs is the originally scheduled deadhead.