Eligiblity of cenvat credit of service tax

in case of transport sector,whether they are eligible to take the cenvat credit  of service tax since as such they arent liable for collecting service tax .There is a notification in this regards that if an assesee takes the benefit of such notification ie. not to collect S.t & also no claiming of cenvat credit.i Would like to confirm the same & also the details of notification 

pls reply asap

regards,

nitin