Evoko Liso uses impersonation as it has many key advantages over delegation which is used by its predecessor, Evoko Room Manager.
Using delegation, each connection made to EWS (Exchange Web Services) is done by a specific account with delegation. This is no problem with smaller installs as the default EWSMaxConcurrency value will allow up to 27 concurrent connections to Office 365. But for larger installations, this requires a lot of service accounts to avoid the risk of connection throttling.
For example, if you had 500 rooms in Office365 where the limit is fixed to 27 simultaneous connections, with delegation you would need to configure 20 separate service accounts. With impersonation, one service account is enough.
Developing the Evoko Liso, making the setup experience more streamlined and straight-forward. Eliminating the impact of throttling policies also made for a more "real-time" experience, with instant feedback from the Liso system.
Using impersonation, only a single service account (e.g. firstname.lastname@example.org) is used for all communication, but from the Exchange server's view it is the individual rooms that makes the connection and therefore there are no issues with EWSMaxConcurrency, EWSMaxSubscriptions or any other throttling policy that could cause unwanted behavior.