No one was harmed in the attack, said Senior Superintendent Roberto Rosales, provincial police director.
The cellsite was manned by just one security guard, whom the attackers disarmed.
Rosales doubted whether the New People’s Army (NPA) was behind the incident, saying communist rebels are not traditionally armed with Armalite rifles.
This, despite reports that the attackers shouted "Mga NPA kami (We are NPAs)" when they fired their guns.
Rosales said groups opposed to the setting up of the cellsite in the area may be responsible for the attack.
Earlier, a group of workers hurled stones at the premises reportedly to harass the Japanese company contracted to build the transmission facility.
Police were also looking at the possibility that the attack was meant to discredit the cellsite’s security agency. A number of security firms were reportedly vying for the service contract.