Need more information. Type of scanner you are using for starters. Not sure what you mean by 'code' either... EMS is on the Fleetnet trunked system.... so to properly listen in you will need a scanner that will do VHF trunking.
I'm pretty sure its something with the programming of the scanner, but if not.. here is some info for ya.
I have a buddy that lives out in Simcoe... I have no clue what it is out there, but we found he had reception issues as well- (indoors and outside with a weather radio) We could not receive ANY of the weather channels at all at his residence, or anywhere outside his residence.
Walk down the hill to the shop (yes his house is on a hill) and plugged in the radio there- worked fine.. Which makes no sense at all.
We ended up mounting a external wideband scanner antenna on a pole, strapped to the chimney. (it doubles as a "lighting rod" as well I am sure) We ran the feed inside, and its just a "half" strength signal, but at least he has reception now.