I have been employed with ESI dealers and installed and maintained these systems for over 10 years, the ESI Presense Management feature and how it works is very unique to that system... it is deeply integrated into the system and it's user based call routing functionality, the FOBs and door boxes actually do much more than just put the phone into DND when they FOB out, the system also logs all these actions and they can be reported on and used to import directly into time and attendance software solutions. It also ties into their UC client (VIP) for showing presence and station status (Off-Premise is different than just DND, Off-Premise can route calls to a cell, well DND can route to Voicemail, or whatever the user choses as a destination based on the status of the phone). The FOBs and door readers are also totally configurable, the FOBs are assigned to users/stations, which also gives them access to certain doors at certain times of the day or days of the week. It is a much more encompassing solution than it appears, and it is all controlled by the phone system.
Honestly, I have never seen another phone product that can emulate what it does with the door readers, cameras (which can be integrated into the door box system with recording of video), call recording, etc... The ESI is not without flaws, but some things like these it does extremely well and we have not found a solution for Mitel or Avaya platforms that can achieve the same results.
Sorry, but they need to change the way they do things and use MiCollab Client properly or find another solution. Most of our ESI customers won't even consider a different platform.
Probably not what you wanted to hear, sorry...