Are master's degrees from IGNOU acceptable for admission into Ph.D. courses in top universities?

It is not only accepted, but it also falls into the H+ category. The H + classification simply indicates that the degrees earned at this institution are transferable to the university sector. It has nothing to do with a preliminary decision on whether this institution's qualifications can be equated with German higher education qualifications. It should be noted that no equivalence determination or evaluation of higher education institutions in Anabin occurs on the Status down. 

Contrary to popular belief, the question of whether a foreign institution corresponds to a German university or a German university of applied sciences is not answered. In the field of higher education, equivalence definitions and assessments are conducted solely in terms of final types and degrees.