07 October 2012
If each project is divided into several sub projects and each sub project is assigned to sub contractors who provides services INDEPENDENTLY, then exemption can be claimed. And in your question it seems that there is lack of independence for the sub contractors as they are just providing services to the main contractor. Hence exemption cant be claimed.
08 October 2012
so if contractor enters into agreement for providing service then he can claim exemption & if only service received then he cant claim exemption.