We are currently installing a Swyx system, that is fairly straight forward, no training course needed for the setting up of the server, but the hardware, especially the Mediant which takes the VOIP signals and converts them into analogue for legacy devices, like fax machines, and BRIs for connecting to the ISDN trunk, is not so simple, although it still doesn't need a 2 week training course.
But to know the system inside and out, in the case that there are problems that are not so straight forward, that is why you need some training. We are doing on-the-job training, the telecoms engineers are making the initial install and we are ghosting them. Seems to be working so far and should be sufficient for maintaining the system afterwards.