When a customer hands over their equipment to another party there are normally a number of obligations which both parties agree to. It is not unimaginable - having drafted several of these for a very large chain of stores in the UK - that part of that agreement allows for the replacement of components at the engineer's discretion and without a requirement for parity of either cost or specification. In simpler language, the engineer could, depending on the arrangement and within reason, do whatever he felt necessary to fix the problem.