SMS is more of vestigial debug feature of GSM that was brilliantly commercialized than anything that has to do with SS7. And by the way SMS is out of band on the backhaul network, not on the air interface (and the whole SMS protocol on air interface is horribly complex and inefficient, it essentially involves building data call that passes SS7-like messages, typically one per such "call" in each direction, another funny fact of this technology is that address fields in these messages have larger maximum size (256B) than than actual SMS contents (140B)).

But when one wants to take SS7 into this dial tone discussion it is important to note that traditional SS7 call flow (INITIAL ADDRESS/SUBSEQUENT ADDRESS/ADDRESS COMPLETE) is designed for normal incremental dialing and not cell phone style number at once then send style. I'm too lazy to look it up but I believe that GSM's ISUP/DSS1 derived on air signaling protocol is capable of that too (although I've never seen device that allows user to do that). Relatively common user experience problem with VoIP deployments I have seen is that this is effectively impossible with SIP and user has either to explicitly end dialed number with something or wait for some timeout.