Hi
Which CUCN release are you on? I've been fighting with this myself as you may have seen from my previous threads. I then filed a case, and it appears this is supposed to work, but is broken in 10.5.2 - I was told I could roll back (but can't as this breaks AD integration if samaccountname changes), or upgrade the 11.5 when it's done.
There's a defect you can track: CSCuu97867. I'm waiting for an ES on 10.5.2 to get this functionality as I need to convert users. Basically, you can change the LdapType just fine, but the API doesn't make the corresponding changes to LdapCcmUserId and LdapCcmPkid (unlike the GUI where it does just that to convert a user).
As for showing up in the import - I suspect once this is fixed, you'd still have to wait for an AD sync cycle before things are done.