In some programs yes, and in some programs, no.  The paymaster we use is mandatory for certain programs because our group has had tremendous success with him for years.  He has an international reputation for efficiency, fairness, compliance, honesty, timeliness, reliability, and accuracy on payouts to everyone - - from clients to intermediaries and anyone else contractually agreed upon to be included.  It surprised us that he is even favored by the Zurich program in Switzerland.  You would think they would have their own local trusted paymasters, but they use ours!