TangoCMS

$url = $this->_router->makeUrl('something?foo=bar');
There is no slashes in this path, so makeUrl will not treat it as a path. It will rather make a new instance of Router_Url (with no constructor arguments) and insert the one argument ('something?foo=bar') as a module with Router_Url::module(). Hence the "path" won't get parsed - the query string will not be saved nor extracted.

Same thing goes for fragments (#).

However, this will work as expected:
$url = $this->_router->makeUrl('something/again?foo=bar');
because there is a slash in the path. makeUrl will treat is as a path and hand it over to Router_Url which parses it.