I successfully called a BO: BAQ with another user on Customziation this way you can try with other BO
Session session1 = (Session)this.oTrans.Session;
string url = session1.AppServer;
Ice.Core.Session session2 = new Ice.Core.Session(“username”, “password”,url );
Ice.Proxy.BO.DynamicQueryImpl BQAEX = Ice.Lib.Framework.WCFServiceSupport.CreateImpl<Ice.Proxy.BO.DynamicQueryImpl>(session2, Epicor.ServiceModel.Channels.ImplBase<Ice.Contracts.DynamicQuerySvcContract>.UriPath);
// DynamicQueryAdapter BQAEX = new DynamicQueryAdapter(oTrans);
//BQAEX.BOConnect();
QueryExecutionDataSet qds = BQAEX.GetQueryExecutionParametersByID(BAQID);