AT&T stock (T) rose more than 7% on Wednesday morning after a court filing late Tuesday provided details on AT&T's exposure to lead-clad cables and offered some initial insight into the potential cost of removing these cables.

In separate notes to clients published late Tuesday and early Wednesday, analysts at Goldman Sachs and Morgan Stanley both estimated that the removal of these lead-sheathed cables could cost AT&T up to $4 billion.

Both firms noted AT&T market's cap had fallen by nearly $15 billion through Tuesday.

Shares of AT&T, Verizon (VZ), and Frontier Communications (FYBR) all rallied on Wednesday following AT&T's disclosure late Tuesday.

Goldman Sachs analyst Brett Feldman and his team used Tuesday's court filing to extrapolate the cost of removal for lead cables "neither buried nor in conduit."

The estimated cost for about 60,000 miles of cables sits in a range of $2 billion to $4 billion, per Goldman's estimates.

"This illustrative calculation does not factor in time (i.e., it would likely take several years to complete a project of this scope) nor the potential to share these costs with other projects such as AT&T’s ongoing deployment of fiber," Feldman wrote in a note on Tuesday night.

Morgan Stanley equity analyst Simon Flannery also estimated potential costs of $4 billion.

The analysis comes after several Wall Street firms downgraded the telecom stock following a Wall Street Journal report that showed the telecom giants' historical use of lead-covered cables is contaminating many parts of the country.

Analysts at JPMorgan had previously downgraded AT&T as the potential liability from the lead cables was "unquantifiable."

On Tuesday, AT&T responded to the Wall Street Journal's report by providing access to a court filing from Pacific Bell Telephone Company, a subsidiary of AT&T.

The filing includes a footnote that states AT&T estimates lead-clad cables represent less than 10% of its copper footprint, which includes about two million sheath miles of cable.

The filing also provided details on the estimated cost to remove some Pacific Bell Telephone Company cables in Lake Tahoe. Goldman Sachs assumed that the roughly $34,000 to $69,000 per mile cost listed in the filing would be on the more expensive side given those cables are underwater.

Goldman's call for an overall cost of $2 billion to $4 billion is based on that cost adjustment spread across 60,000 miles of lead-sheathed cables that are not buried underwater.