Dwayneg,
How reliable is your information; I hope that it is really good? The last thing I heard before the old Inter-Tel Tech support was let go a few months ago was that it was no longer being updated. The latest version is 4.5 and it works great on Windows XP, Windows 7, and Server 2003. I have had problems with it working properly on Server 2008 and above though, but if you don't mind getting in to the registry files that can be fixed, but you still can not run it as a service and sometimes it still locks up.
Gssieg,
The 5000 has never support redundancy or resiliency so I am kind of think what your vendor was doing was supporting your 2 largest sites and splitting your trunks up between the two. Of course I do not know how they engineered it, but that would be my first guess.
Usually what I run into is that some people, and I am not saying this happened to you, get the Mitel 5000 and the Mitel 3300 features mixed up. The 3300 MCD does support redundancy, resiliency and the sharing of licenses which gives it an edge on the 5000 for obvious reasons to customers who are looking for that.
Other than that the 5000 is a pretty solid piece of equipment and should be able to do more than you will ever need it to do and in my opinion is a good purchase for any company.
Thanks,
TE