Export Related Service_BAS

Please advice for below said query..

A is engaged in the Weighbridge Service & registered with Service Tax department under the category of BAS.

Now one of his clients B denied to pay service tax & argued that they are exporter & are not liable to pay service tax. When A again argued for Service Tax B agreed to give the Letter that all this service they are using is connected with Export Only, hence he is not liable for Service Tax.

My query is the Quote "Export Related Service" will be applicable in the case of Weighbridge Service??

Kindly answer the same with appropriate rules or Notification...