Yes, it is perfectly possible as long as they meet all the medical and psychological requirements. Even if the intended parents have a surrogate and there's no need for being matched through an agency, she has to meet minimum criteria to be eligible and agree to sign a contract.
Read the full article on: What Is a Surrogate Mother? – Everything You Should Know ( 89).

Andrea Rodrigo
Bachelor's Degree in Biotechnology from the Polytechnic University of Valencia. Master's Degree in Biotechnology of Human Assisted Reproduction from the University of Valencia along with the Valencian Infertility Institute (IVI). Postgraduate course in Medical Genetics.