We have teams enabled in our office 365 business premium package. We are able to message and make video calls internally. In the teams and SFB admin centre we have both external and guess access enabled.
However when we search for external contacts (either by email or skype address), we get a message saying unable to find contact. We once managed to find a contact by email address but then got a message to say the contact was offline - even though they had skype up and running.
Conversely Skype users are able to find us by email address but are not able to connect. When they try to make a video call into us, they get a message to say the user is offline.