A forum page over on O2 Ireland's site indicates that they are currently testing the Samsung ATIV S on their network. The post says that testing began on December 4 for both the ATIV S and the HTC 8S. It isn't clear just how long the testing process will take, but it may be an indicator that both phones are very close to being released.
The Samsung ATIV S was the first Windows Phone 8 device announced and the last to show at the party. For reasons still unexplained, it has been delayed, with rumored release dates ranging from the end of December to sometime in February 2013. Windows Phone Central received a communication from Samsung saying that the ATIV S was still on track for the "end of the year."
O2's testing of the device and appearances of ATIV S-related advertising materials various retailers' ads and stores both seem to corroborate this, though it still remains to be seen. Samsung was quick to throw their hat in the Windows Phone 8 ring, but has since been left in the dust by HTC and Nokia, who have both released hero and mid-range phones, along with massive marketing campaigns. Samsung is clearly focused on the Android market, but if they hope to get any significant slice of WP8, they had better get a move on.
Source: O2; Thanks for the tip, Skunkwurx!