Traveled on a N fare CPT-DOH-ZAG last Friday with a 8 hr 10 min layover. Called QR two weeks prior to travel to confirm STPC, which was verbally confirmed and was told to check email for voucher. Called QR a week later to inquire about STPC status, again confirming eligibility and told to expect email voucher by 24 hours prior to departure.
On day of travel: No email from QR upon departure, so upon arrival in DOH, proceeded to transit desk and was told that I was ineligible. Agent was confused, called manager over, and after some fiddling, showed me a printout with the condition that the fare for the entire segment XXX-DOH-XXX had to be at least $400USD. After a bit of arguing (after having confirmed eligibility twice before the trip), the agent suggested that I make use of the utterly disgraceful (non-Al Mourjan) business lounge for the next 8 hours.
So, for those traveling in cheap, but seemingly eligible Y tickets, make sure the base fare for the segment is at least $400 USD.