Apparently
Cotag is more secure than standard 125 kHz technology because the content on the card is protected and there
is no equipment available outside Siemens to copy or tamper with the cards.
However
But more interestingly, this Proxmark forum post
http://www.proxmark.org/forum/viewtopic.php?id=1258
Which is an old thread (2013)
But there now seems to be some Proxmark commands… on the Iceman fork at least
lf cotag read