I've certainly come across bits and pieces of evidence for this kind of practise, and I too have thought how interestinhg the phenomenon is, and how one would love to explore its mechanics further. Writing from memory: when an early miracle was attributed to Thomas Cantilupe, bishop of Hereford, in the late C13, news of it was quickly copied into documents that were distributed throughout the parishes of the see for announcement at the pulpit. Numerous bits of English political news -- which battles the king had won or lost, etc -- were likewise spread from bishops to local pulpits in the c15. When Henry IV excommunicated Archbishop Scrope of York, Archbishop Arundel of Canterbury 'passed over' his obligation to have the announcement made from every pulpit in his Province. There are many such: clearly the clerkly wheels were well oiled, the distribution networks reasonably effective. Fascinating.

Jon