Thanks to Jamie Stark for the heads up, Microsoft have updated their Service Level Agreement for Microsoft Online Services document to include Skype for Business Online, PSTN Conferencing and PSTN calling.
You can download the document here:
Three SLA’s can be found in the document (at time of writing)
Skype for Business Online Service Level Agreement
Skype for Business Online – PSTN Calling and PSTN Conferencing Service Level Agreement
Skype for Business Online – Voice Quality Service Level Agreement
Poor quality calls are classified as bad using the following packet loss metric:
It is interesting that the voice quality SLA is only for calls on a Skype for Business Certified IP Desk phones on wired Ethernet (I would guess to easily rule out PC/driver/headset issues) and only includes the network segments Microsoft are responsible for (makes sense).