I apologize if this was asked and answered, I looked but did not find 
Do we have the ability to interact with groups over SMS such as for a group of coworkers?
If yes what is the maximum capacity?
I am thinking of a chat group for my team of eighteen individuals. We had been using an xmpp solution but groups on that protocol max out at less than that, ten participants if memory serves.
Hello Trifle1767,
At the moment SMS/MMS capabiities does not include group interaction, currently only a traditional usage is offered , for more information, please check https://wiki.voip.ms/article/SMS
Trifle. further to Willliam’s reply, your colleagues with conventional SMS can include you in their group SMS. You will receive the SMS to the group. However, you can either respond to only the sender, or for for every reply you send to the group, you have to add all the recipients in the field “Please select or type a contact number”. Note, your outgoing SMS are individual messages to those in the recipient list, if your colleagues reply, it is only to you.
At the moment there is no information in this regard, ill highly recommend to add this as a feature request through https://www.voip.ms/m/features.php
Just did so. 