Like if and when this pair is rarely if ever justified ; one by itself would meet the case. It might be argued that as and when is an appropriate expression to use of something that will happen piecemeal ("Interim reports will be published as and when they are received") but the argument is not convincing: as by itself would do. Nothing can be said for the use of the pair in such a sentence as :
As and when the Bill becomes an Act guidance will be given on the financial provisions of it as they affect hospital maintenance.
Bills cannot become Acts piecemeal.