Does Xfinity Home Phone service provide a true landline?

I live in a building which requires a landline phone plugged into a wall jack.  Is it possible to set this up with Xfinity home phone service?  I already have internet and TV service; I see 2 "Tel"jacks on the back of the gateway, but it's unclear from my research if these only provide VOIP service or if I can connect them into the wall and activate the rest of the wall jacks.  Thanks in advance.