Removing holes is generally regarded as a good thing in ATM.
If they can't be removed or plugged, then some kind of operating practice/tips/auto-alert thingy provided to mitigate a perceived high risk situation.
This has been an evolving practice in a lot of ANS providers since day one, hugely aided (and at the same time made more complex) more recently by technology.
Unfortunately it seems to me that in mitigating against a lot of these "gotchas", the exposure of the human element in dealing with unusual or non-standard procedures has become very limited.
In ancient times the "non-standard" was almost the norm, most were well practiced at dealing with it and the tools used were regularly dusted off and given a work out. There were other "gotchas" that could catch the unwary out, but I believe the operating environment "way back then" cultivated and encouraged a different order of situational awareness and maintain-a-good-scan type mentality.
With the more systems-based technology we are now using it is more likely in my opinion that doing things in a non-standard manner, or approving a non-standard operation rarely is more likely to be risky than approving it (space and procedure permitting) either more regularly,
or not at all. Ever.
It's my view that it's best to not try and come up with rarely used procedures aimed at mitigating risk for infrequent situations. The procedure will be forgotten unless called on regularly. If it is in a QRH, one has to remember and know there is a procedure in the QRH, then look for it. And at the same time the OS still requires monitoring, there is often less time and attention available for dealing with ancillary tasks.
Not a thing to want to be doing (if applicable) at 2.52 in the morning.
Either (1) make the procedure routine enough, and train for it, so it is almost instinctive to carry out safely, or (2) never use the procedure. I think ATM generally is moving toward option (2).
Whether that is the correct direction to be moving, I don't know. In my experience, sooner or later, there will always be a legitimate and sometimes pressing requirement to handle something non-standard.
Originally Posted by A380-800 driver
thank goodness for TCAS!!!!
I say thank goodness to an alert flight crew that had the situational awareness, and the luxury of a common language, to query it.
Without wanting to second-guess the result of the inquiry, that was possibly the second last hole in the cheese.
Originally Posted by waren9
<Worlds best pract..............and all that.>
That's where we're all heading. 
[edit to add:] My comments, in case it is not obvious, are concerning occurrences of this type, particularly where a non-standard element is involved, generally. I have no inside knowledge of this one, nor of the way area control is performed in Australia.
I think it is high time a holistic overview of training/technology is entered into.