I live near Eglinton and Chaplin in Toronto. Recently my LTE signal has gone from 2 bars in the house to 1 or 3G (no LTE). This only started happening about a month ago after working OK (max 3 bars in the house) for years. This is with various iPhone 5S devices running IOS 8.3 .
Please report this to the network/tower group as it only just happended and appears as if some tower is not broadcasting LTE any longer. There is construction for the Eglinton subway in the area but I'm not sure if that's related or not.
I am sorry to hear of the LTE issues in your area.
You did mention that this issue has been reported with various iPhone 5s devices. Have you noticed that this is happening with any other type of device out side of the iPhones? Also have you tried a different/new SIM card?
My iPhone 5S works perfectly in many other areas, including my office, where I receive 4 out of 5 bars consistently. It has only gotten much worse recently. My signal in Field Test Mode on the iPhone is as low as -126.
Some change in Tower signal or interference has occurred. Can you please report it to your network people?