Can a vengeful CCJ creditor pass the debtor's car registration to bailiffs?

Yes

The bailiff can take control of goods provided they are owned by the debtor.^[1]

Bailiffs cannot take control of any vehicle that is on hire-purchase or leased,^[2] or parked on any private land that is not a highway.^[3][4]

^{[1] Paragraph 10 of Schedule 12 of the Tribunals, Courts and Enforcement Act 2007

[2] See: Bailiff clamped or towed your hire purchase car

[3] See: Bailiffs take a car from private land the debtor does not live or trade.

[4] See: Protecting your car from bailiffs}