When Toronto was amalgamated, the transition team left the issue of duplicate street names to the new Council. It was a political hot potato - no community wanted to lose their Church Street or George Street. No Councillor was going to earn points in the ward by being reasonable or compromising on this issue. The issue bounced around for a few years, with various staff reports, until it was finally abandoned as unsolvable. Misdirected ambulances and fire trucks be damned.
When Ottawa was amalgamated a few years later (2001?), its transition team dealt with the duplicate street names and, having seen what was happening in Toronto, avoided leaving the issue to the new Council. People hollered and were upset, but in the end they looked to preserve street names by adding new words (e.g. Church Street in North Gower became Village Church Street, etc.) and most residents were relatively mollified and the issue died down. And Ottawa doesn't have the same 911 problem today as Toronto does because Frances Nunziata was convinced that the Church Street in Weston is more famous than the Church Street downtown.
ETA: I just realized that I responded a post from 6 months ago. Sorry.
