if they are down, you don't have internet access.
if they are not filtering anymore (maybe default setup is "no filters" instead of "no access" like when openDNS website is down) then everything pass and you get the update.
it depends how the default filtering method is configured, and like said on first post : the filtered list can change without notice.
the owner can just decide to stop serving these filters, or block other URLs without notice.
It's great to have someone helping others, but if you want a perfect solution you should set your URL blocking yourself (local proxy, or deleting the update folder)
relying on someone else for security is not recommended, as good the intention is from that user. (I'm not criticizing, just pointing it's always safer to manage things yourself)
note that you can update your console if you already have haxchi installed.
and even if you don't and the console update itself, the current version (5.5.2) can still be hacked.