Lien was seen leaving his building with a woman believed to be his mother or mother-in-law shortly after noon on Friday.
The two did not answer Nina Pineda's questions, before entering a high-rise building in Manhattan.
Four of the bikers accused of taking part in the attack on an driver on the Henry Hudson Parkway are appearing in court Friday.
The court dates come as investigators work to determine what role other bikers may have played in the assault.
Bikers Reginald Chance, Clint Caldwell and Craig Wright, as well as Officer Woljciech Braszczok, are or will be appearing.
Chance was in court Friday morning and became the second person indicted in the case after Robert Sims, allegedly seen on video opening the door of the SUV and later beating the driver, was indicted Thursday.
Braszczok was next, entering and leaving court with a hoodie over his face. His case was adjourned until February to give him a chance to testify before a grand jury.
Caldwell appeared next, and his attorney says he will testify before a grand jury next week, so he was not yet indicted.
Wright was expected to appear in the afternoon.
Suspect James Kuehne, who prosecutors say struck SUV driver Lien over and over with his motorcycle helmet, was in court Thursday. His attorney pleaded not guilty, saying his client is distraught over the accusations.
Sims, Kuehne, Wright and Caldwell are all accused of assaulting Lien after he ran over a fellow biker, Edwin Mieses Jr., who suffered leg and spine injuries and may be paralyzed.
Lien told police he feared for the safety of his wife and 2-year-old daughter, who were in the Range Rover with him.
Braszczok, Chance and Christopher Cruz also face charges, but prosecutors say they did not participate in the assault.
There may have been two other officers riding in the group, as well.
Uniformed officers, even off duty, are expected to jump in if a crime is occurring, but rules are murkier for undercover officers, who face blowing their covers if they come forward.
Lien hasn't been charged with any crime.
Meanwhile, some bikers are suggesting Lien, knowingly or not, instigated the confrontation off-camera earlier by clipping one of the bikes.
Authorities are looking into everything that unfolded along the ride's path from lower to upper Manhattan, including the possibility a motorcyclist hit the SUV, not the other way around, and broke its side mirror before the encounters on the video, said a law enforcement official, who hadn't been authorized to discuss the inquiry and spoke to The Associated Press on the condition of anonymity.
Investigators are looking for other helmet-camera videos of the ride, which spurred 911 calls about the bikers' behavior before the SUV driver's beating.
Gloria Allred, the attorney representing Mieses, claims Lien bumped another motorcycle while changing lanes 2 to 3 miles before his SUV knocked into Cruz.
"We have evidence that he hit that (first) bike and didn't stop," Allred said by phone.
Mieses, of Lawrence, Mass., didn't see any earlier encounter but got off his motorcycle to defuse the tense situation and was headed back when he was hit from behind by the SUV, she said. He broke his legs and suffered a spine injury and likely is paralyzed, his family has said.
Allred declined to say what other witnesses had contacted her, but another biker who participated in the rally, Louis Castaldo, gave a similar account in another interview.
Castaldo said that when bikers tried to approach Lien's Range Rover, Lien "decides to run over three or four people. ... He should have just apologized."
Images made public have painted a narrative that begins with Cruz, of Passaic, N.J., pulling in front of the black Range Rover and decelerating to the point where the vehicle bumps his back tire.
Cruz, since his arrest on reckless endangerment and other charges, has insisted he looked over at the driver only to change lanes and didn't deliberately slow down. He didn't see any prior interaction that may have happened between the SUV and the motorcyclists, said his attorney, H. Benjamin Perez. Cruz waited on the highway for police when other riders chased after Lien, Perez said.
"He's treated as though he orchestrated this entire event," Perez said. "It's crazy."
(The Associated Press contributed to this report.)