yes it would or with v4 software they could have 4 ip extensions
With a gateway he will need a second system in the new site
Plus telephones, could be as cost effective to upgrade to a 100 or the new ncp500 either way they will require a data link between buildings, granted the 6-8 ip phones would require more bandwidth

“I have not failed. I've just found 10,000 ways that won't work.”