about EAP-TTLS and EP-TLS yes they are more secure but PEAP is much more common becuase it uses already available credentials and infrastructure most companies already have RADIUS servers and not as many AP vendors sell devices that support or are optimized for TLS or TTLS so PEAP is the de facto standard for WPA enterprise and the most common implementation of 802.11X and about the recon aspects if you read the wikipedia article on APTs it reads
Advanced persistent threat (APT) usually refers to a group, such as a foreign government, with both the capability and the intent to persistently and effectively target a specific entity. The term is commonly used to refer to cyber threats, in particular that of Internet-enabled espionage, but applies equally to other threats such as that of traditional espionage or attack
and i bet the FSB, PLA or Iranian Revolutionary Guard could easily and have gotten people into the U.S. or Europe to do B&E so this is just taking it a step forward (or in some cases a step back) and a lot of that recon can be done with OSINT sources, a lot not all. and NACing or DMZing is not a 100% fix all they have to do is pop a computer connected to the wifi but also has a Ethernet connection to pivot and if they use PEAP (which most of the companies where i live do) they already have a set of credentials for the other machine on the network not just the wifi, remember most PEAP implementations use the same RADIUS servers as windows login and even if they don't there is password re-use and derivable attacks. also most APTs have access to HUMINT resources so paying a janitor to re-arrange a few cables to create a bridge into the internal network would not be to hard albeit risky and i don't think they would trust a janitor perhaps a crooked IT person, that is another thing APTs could recruit insiders to do the B&E work as 3xban mentioned and for the being stealthy part some one sitting in a van down the street is pretty common place where i live and most cities. also most IDS and IPS excluding WIDS/WIPS solutions focus on connections inbound from external sources and in some government and intelligence agencies i would imagine they could not sniff or log traffic for sensitive departments or projects making a physical access or wireless attack even more stealthy. one of the main problems i have with the infosec and physical security departments in most organizations is they don't work together when they should what good is a strong network based camera and door swipe card system if its control computer can be found via shodan (
http://www.shodanhq.com/search?q=GoAhead+Webs+login.asp+no+cache%2C+must+revalidate) and uses ancient software? whats the point of having a multi thousand dollar IDS/IPS solution if its host box's power source can be cut from outside the building? we need to start working with the physical security people more then we do right now, the navy and the army have the marines for a reason.