Hi @mjs243 thanks for your post here in the Community - welcome!
That is generally correct yes, once the adaptor is sent and the switchover is complete, the landline should work through the Hub for you automatically.
If you've been scheduled a switchover appointment though, it is best to keep this in as the technician can make sure everything's working for you as sometimes, there needs to be work at the cabinet if this isn't successful so it saves you the possibility of calling up again, to re-book this in if things don't work automatically.
Please let us know however, if you do need any further help!
Many thanks
Tom_W