I don't have any selective withdraw privileges.  Mine are the same as those of any other verified user.

Using what I have learned by experience and by filtering useful information from public fora over many years to have a greater chance to succeed when I try to withdraw is not the same as selective withdraw privileges.  Not all my attempts were successful, btw.  I made a number of 10 BTC withdrawals.  Some were successful, some not.  I did it at a time when I had reason to expect a higher success rate, based on public information and my own experience. 

In this case people came to #mtgox and complained about an error message which usually means the bitcoin address entered in the withdrawal form is invalid or indicates an empty hot wallet at MtGox.  This was at the middle of the night Tokyo time, and I knew they would fill up first thing in the morning.  After a couple hours the reports stopped coming, and this would be the sweet spot.  Hot wallet refreshed with old unspent inputs which most likely would be chosen first.  They don't keep dust in their cold wallets, so I could choose a reasonable withdrawal size as well.

No special privileges or access to restricted information needed.  Everything is out in the open for everyone to learn.  I am certainly not the only one unaffiliated with MtGox who used this trick.  The fresh inputs went very quickly.  My only fault here is telling you about it.

At least MtGox credited my failed withdrawals back to my account.  The 8 BTC withdrawal I made from Bitstamp this morning is still listed as "Finished", but nothing arrived, nothing credited back and support are quiet.  AFAIK Bitstamp has no IRC support either.