Is there a way to convert this into a "City" so that e.g. random road can be used with the symbols?
No, there is no way to just convert it.
Of course, it is possible to define house shapes in the style used by CA09, they are quite simple after all, and use the tools with these, but be aware that the random street command doesn't use symbols, it uses randomly drawn houses for more variety.
You may be able to use the Symbols Along command with the house symbols though, that's not quite the random street command, but it has similarities. For that command to work, the symbols need to be part of the same symbol group, something I did discuss in my latest blog entry.