Employer has no authority to grant any exemption , he has to maintain the rules of establishment of coverage and contribution.
at the time of getting "smart card" the employee may declare his / her status of CGHS to ESIC officials and if the ESIC will get it in order they may attach the both in single row, (usually both run parellal and does not get attached mostly) so that he would not get any lapse of benefit of either
but this does not makes him/her to exemption from contribution