TORONTO — An Ontario judge has agreed to hear a Charter of Rights challenge brought by Telus and Rogers after they were asked by police in April to release cellphone information of about 40,000 to 50,000 customers as part of an investigation.

Justice John Sproat says that the case has highlighted important issues about privacy and law enforcement that should be challenged in open court, even though Peel regional police tried to withdraw the requests.

"The privacy rights of the tens of thousands of cell phone users is of obvious importance,'' Sproat wrote in a ruling dated July 16 and released on Friday.

"Counsel for Rogers-Telus will be able to identify and argue Charter issues that might not otherwise be evident.''

Mobile phones need to make wireless connections with antennas that are often mounted on towers. A record is kept each time a phone attempts or completes a phone call, text message or email that identifies which tower made the connection. Sometimes a call will be transferred from tower to tower, providing information about the phone's movements.