Yes they can give traffic information if requested to do so
Air/Ground (A/G) - A two way communication between an aircraft and a ground station in which the ground operator may only pass advisory information regarding the situation local to the aerodrome.
See also CAP 413, chapter 4, pages 32-35
5 Aerodrome Air/Ground Communication Service Phraseology
5.1.1 ..... It is not only the means by which information is passed but it also assists pilots in maintaining an awareness of other traffic in their vicinity
5.2.3 An AG radio station operator is not necessarily able to view any part of the aerodrome or surrounding airspace. Traffic information provided by an AG radio station operator is therefore based primarily on reports made by other pilots. Information provided by an AG radio station operator may be used to assist a pilot in making decisions