Get list of canonical urls?
I'm running into this problem, though I'm not sure we're using Path Redirect. For me, Migrate is bringing in URLs that are non-canonical, and I need to override the query to get the URLs that D6 has decided are canonical.

In D6 the code that does this is drupal_lookup_path('alias', $path);

By examining this I determined that if you don't care about language, the bare query is (for node/121):

SELECT dst FROM url_alias WHERE src = 'node/121'  ORDER BY pid DESC;


The ORDER BY pid DESC is the key part here.