My point stands: if you spend the money to replace a bus with a streetcar, and make no unrelated changes, this area that can be reached in a given amount of time doesn't expand, at all, for anyone.
I strongly suspect that if a lot of people didn't have the (false) notion that streetcars improve mobility (e.g. by being faster or more reliable), streetcars would not trigger redevelopment to the extent that they currently seem to do. To the extent that they WOULD still do that, I'd argue that that would make the streetcar a possibly worthwhile civic amenity -- exactly like brick paving or public art -- but not really a transportation project.
As I've said there's a lot more to access than mobility, but by definition, mobility is the kind of access that transportation projects provide. That's why we call it transportation, no? Moving things from one "port" to another. By all means, build your streetcar as a civic amenity if you like, but call it that, use funding sources designed for that purpose.