Last year the IRS has won a John Doe summons for debit card information of SML customers with offshore accounts suspected of being used for tax evasion:

https://www.forbes.com/sites/robertwood/2017/01/25/irs-hunts-debit-cards-for-tax-evasion-as-court-approves-john-doe-summons/#556d42b738bf

It is not beyond the realm of possibility for the IRS to demand BitPay or Metropolitan Commercial Bank (the card issuer) for debit card transactions of BitPay card users.