AM Tower Too Hot for CDMA Co-locate

What Now?!? writes:
Working on installing a 1900 MHz CDMA cellular station co-located with an AM station, we have found what seems to be an insurmountable problem.

The 250' tower is home to an AM station and it seems the tower itself is part of the antennae, either by design or accident. Regardless, while the contractor was trying to bring the coax into the building the shield of the coax arced to the metal skin of the building. The building is, of course, grounded and electrical work is good. The coax shield is grounded to the tower normally. The tower is not isolated but is said to be grounded. While investigating the problem, both AC and DC voltage measurements proved futile as the DVM overloaded when measuring in either mode across center conductor and earth ground and shield and earth ground. There was almost no difference in potential between the center conductor and the shield, indicating a lot of power being induced across both.

In short, it seems the tower's ground is hot. Hoping I have provided enough information, does anyone have any idea on how to salvage the project? Right now it seems we have to look for a new site but we are trying to avoid that as the site offers a worthy geographical advantage.

Thanks...
What now?!?