IT needs to setup 301 redirects from the OLD pages to your NEW Marketo pages.
Alternatively they can do this for the entire OLD subdomain.
You cannot use Marketo's redirect rules engine to do this for non marketo pages.
Dan, do you know how long it takes for it to start working? I know sometimes it take a bit for it to be recognized on the web.
Unless your DNS CNAME entry had an abnormally long TTL (cache expiry) a DNS change would be felt worldwide in under 48 hours. Wherever the entry is not cached, it always takes effect immediately.
What's the CNAME?