I guess TeliaSonera has never heard of SONET rings? More likely they made a decision to go cheap. All that self-healing fiber-optic ring stuff costs money.
They probably are just doing 10Gb Ethernet over fiber, and they bought either one or more wavelengths on top of DWDM provided by Cogent. Cogent themselves do not do SONET, instead, they rely on Ethernet plus routing.