I am not familiar with Microsoft Sync. This article gives some info, but Sync is too broad of a method to isolate if they can see your traffic or not. My guess is probably not. They might be able to see traffic coming from the work computer, but as long as you don't have a VPN client or server, traffic from other devices on the network should be unseen.
If privacy is a main concern, I would suggest asking your work's IT. Word it in such a way, such as family members playing games, so they don't get suspicious. Or you could use a VPN client like OpenVPN or LogMeIn Hamachi to secure the traffic, that way they can't see what it is even if they can see where it's coming and going from. See here for more info on free VPNs.
Edited by Trikein, 17 December 2016 - 01:58 PM.