I sent an email with that URL in it and it didnt get tagged.
Well, it won't get tagged by SA based on that alone. There are very few "sure fire spam" rules in SA, and none of the SURBLs are on that small list.
What you need to do is look at your hits list for the message, and see if it matched the SC SURBL rule.
If you're using SA 3.x it should show up as URIBL_SC_SURBL in your hits.
If your setup doesn't put the hits list in some message header even for nonspam, you'll probably have to do it manually using spamassassin -t on the command line.
You can also send that URL in an email that also contains a GTUBE string. The GTUBE will force a spam tag, and presumably then your setup, no matter how strange, should list out all the hits. You should make sure it hits both the GTUBE rule and the SURBL rule.
http://spamassassin.apache.org/gtube/