No, a doctor who has been asked only for a consultation cannot take over the case. Section 4.3 of the Indian Medical Council (Professional conduct, Etiquette and Ethics) Regulations, 2002 talks about this:

“4.3 Consultant not to take charge of the case: When a physician has been called for consultation, the Consultant should normally not take charge of the case, especially on the solicitation of the patient or friends. The Consultant shall not criticize the referring physician. He / she shall discuss the diagnosis treatment plan with the referring physician.”