Dissident republican gunmen armed with Kalashnikov rifles launched the attack from a makeshift platform as a convoy of police vehicles drove past the Ardoyne’s Brompton Park in December.
None of the police officers were injured during the dusk attack at the top of the Crumlin Road.
In follow up searches, police recovered two high powered rifles abandoned by the fleeing gunmen.
During dawn swoops on Tuesday, detectives arrested a 41-year-old woman and a 43-year-old man in the north Belfast area.
However, after several hours of questioning at the serious crime suite in Antrim, the pair were released.
Detectives are to forward a file to the director of the Public Prosecution Service for his consideration.
They were later released pending reports to the Public Prosecution Service.