No, the cards cannot be examined. But with audience management, it shouldn't be a problem. Either way, buy the trick; it's one of the greatest packet tricks ever invented. However, if you want a trick which is examinable, check out Megawave by John Bannon. Not exactly similar to Twisted Sisters but very close.
Which ever one you go for, you are going to learn an amazing packet trick which will astound your audiences.
It is not examinable but it is very strong and has a kicker ending that drops jaws. I use it all of the time. You won't regret the purchase. I close my close up show with it. I know Toby on here uses Bannon's Duplicity which is very similar and the cards ARE examinable.