There are several Masjids in UK where Azan and Bayans are broadcast via internet. In another words this is called digital transmission.
Sometimes it is reffered to as live streaming.
There are various ways one can broadcast via internet, and cost of installation varies hugely, depending on who wants (i.e. large company/small group/individual person) to include digital broadcasting on their website and what method they wish to adopt.
In all cases it is imperative that the Masjid will need to have a high quality internet/ broadband installed.