The holidays are declared for the establishment, so it would apply to all working in the establishment, be it direct or indirect. Are you working 24X7, then certain essential services are required to be done and the required personnel have to be there. Here, the treatment has to be common for both the direct and indirect workers. At any rate, it is imperative that the statutory provision in this regard is complied.
I have encountered a situation like this, where contract labour were surreptitiously called by Shop Floor officials for duty on the day of Holi Festival and one of them met with a minor accident. It became very difficult to handle the situation.
So if you are calling any indirect worker for duty, please ensure all due compliances