In a recent thread, it came to my attention that there may be exceptions to rules like this in cases where the priest is unable to speak due to illness or physical incapacity. At the moment, I cannot find the thread or the reference which was given.
Edit: I found it:
Canon 930: A priest who is blind or suffering from some other infirmity, may lawfully celebrate the eucharistic Sacrifice by using the text of any approved Mass, with the assistance, if need be, of another priest or deacon or even a properly instructed lay person.