I've seen the report on Austria's silver bullion coin as well, but I have to say that this is a badly researched piece of journalism.

In order to transport the face value of EUR10,000, you have to carry 6,666 one ounce coins of a face value of EUR1.50 each, that is more than 200 kg of silver! The bid offer spread of one-ounce silver coins is at least 10%, and this is a very optimistic assumption. So all in all, that's a hefty price and effort for the repatriation of your tax evasion savings! Remember, we are talking about a border where there usually are no controls any more.

So, this article sounds more like a modern urban legend than a matter of fact. The silver disks are in demand, no doubt, but there have to be other explanations for that.