Currently I'm trying to encourage the City of Ottawa to release data under a suitable license.
It has a responsibility to provide where possible information in the language of the client's choice. Economics plays a part here. Currently it does not have a solution that provides maps in French, the CIO is francophone thus is sensitive on this issue.
OSM can provide a French solution politically this gives me quite a lot of leverage on the licensing front. As a retired civil servant I have used a similar approach before with success.
I researched in the OSM wiki and found a number of examples were two languages were used in a certain area. Normal practice appears to be to use the dominant one in the street name field and the other in a name:xx field. In Ottawa English dominates by roughly 3:1. http://wiki.openstreetmap.org/wiki/Multilingual_names
One reason for this would seem to be to allow electronic searches based on the name field. A number of programs will find a match based on the exact contents of a field. JOSM and Maperitive are examples that spring to mind. The street name entries have had multiple abbreviations of the street name, within the City of Ottawa these have all been standardised to the full qualifier, rd to road etc. to improve consistency.
Street signs have differences even on the same street. Locally Prestwick Drive has a street sign that simply says "Prestwick" and nothing else. Different signs have different qualifier abbreviations apparently depending on the length of the sign, and the number of characters in the name.
French street qualifiers such as rue are always used in lower case. Example rue Sparks or Sparks Street this has been confirmed with multiple sources including a francophone teacher. I haven't come across any correctly entered French names other than the ones I have entered myself.
To me consensus means everyone agrees and buys into the solution. My estimate is that more than 97% of entered street names are in the City of Ottawa area have been entered in English only so I assume that the consensus reached was to only use English street names. Adding a French name field will not interfere with any existing applications that depend on English being used in the name field. Note some streets have multiple segments so these will have multiple entries. Not all users frequent ca-talk. I have attempted contact with all Ottawa based OSM mappers listed on the Ottawa page and have seen no dissension for my approach of adding a French name field, and there has been discussion on ca-talk.
Maperitive has been specifically enhanced to display the street names in either English or French as required to meet the local requirements to make things available to clients in the language of their choice. As by-product it can also be used in other areas where there are different languages in use and the information is available in OSM. I would not like to see this effort go to waste.