Hi megaloman,
Yes Avia Integrated is a legitimate company here in Indonesia. They are currently handling the recruitment for Sriwijaya Air, Merpati Air, and Citilink.
I am currently undertaking the 737 Classic type course with Sriwijaya Air, and was recruited into the First Officer program by Avia Integated.
Any enquiries on Sriwijaya Air recruitment should be forwarded to Avia.
Good luck!