For us, the key to truly functional distributed offices was cutting office/home - office traffic out of the equation; rather moving all storage and services up to the Cloud. All traffic now goes device - Cloud (vertical traffic).
Protocols are standardised, and well documented.
Accessing data on a server from a variety of different client devices is no longer an issue. Busy people rarely have to spend time on connectivity issues. Having engineered a solution, the professionals can now concentrate on their real jobs.
Anecdotally, this does not appear to be the case with organisations with complex site to site / device to site / hub-spoke network architectures for their users to negotiate (horizontal traffic).
As far as phones go, we have ditched physical VoIP phones in favour of Cisco-Accredited softphones from CounterPath. As far as people calling us are concerned, they can call the fixed line number or the mobile number, their choice. As far as we are concerned, life is simplified and more efficient. We don't need additional hardware for the landline phone at work or when travelling, it rings on the smartphone, mobile calling and fixed line calling share the same directory of phone numbers, video calls are available.
I would strongly advise people working at home to keep their office network separate from the existing network. There is so much cr*p in modern homes, they are simply not secure, rather uplink the MX/Z via a LAN port on the existing home network and if you are in professional services, your indemnity insurance would become an issue.