Red Cross Callsigns

[The_Brick]

Hello,

I recently purchased an American Red Cross phone and address directory, and one of the intriguing elements was an inclusion of call signs for each ARC office. My question is, would these call signs be used for communicating with other units via PRC-25 or some other field phone or radio, or utilized for MARS calls, or something else?

Below is one of the addresses/callsigns