C&P Telephone Co. held a groundbreaking ceremony last week for the 750,000-square-foot regional headquarters facility it plans to build in Montgomery County.

The $48 million complex, which will house about 2,400 employes when it is completed in 1984, will replace office space C&P currently leases in 12 buildings in Washington and Maryland.

C&P President Robert E. Allen said the principal reason the company chose Montgomery County over 70 other possible locations was that many of the employes who will work at the complex already reside in the county and in Howard County. He added that C&P already has "an accepted presence" in the area since its Fairland Data Center is adjacent to the new site. The new building will be located on Route 29, between Fairland and Musgrave roads.

Allen also said that while C&P has no plans to hire additional employes, the new buildings can be expanded to accommodate another 1,100 people.

Citing a joint study by C&P and the Department of Commerce, Allen told his audience at the groundbreaking, which included Montgomery County Executive Charles W. Gilchrist and Maryland Secretary for Economic and Community Development James O. Roberson, that by 1985, corporate and personal tax revenues paid to the county as a result of the complex will amount to $1.5 million a year.

The building was designed by Rockville architect Donald M. Coupard and the general contractor will be Whiting-Turner of Baltimore. CAPTION: Picture, Architect's model of C&P Telephone's $48 million regional headquarters building in Montgomery County, which faces on Rte. 29.