Yes. IRS Notice  2008-59, Q&A 33 addresses the question of a dependent being claimed by a former spouse.   
Q-33. Do qualified medical expenses for HSA purposes include the § 213(d) medical expenses incurred by an account beneficiary’s child who is claimed as a dependent by the account beneficiary’s former spouse?
 A-33. Yes.

HSAs are the property of only one tax payer. IRS regulations do not permit transfers from one taxpayer to another under normal circumstances. Publication 504 does address the issue of HSA transfer (full or patial) in divorce situations.  The IRS guidelines described below require legal documentation (an “instrument”) for a custodian to move money from one [...]