Tech Central Tracker looked old fashioned a decade ago and is pretty much a living fossil. I struggle to understand why they persist in keeping it on life support. Surely in the M&A activity they've done in the past 10 years, they've picked up a company with a better customer-facing helpdesk than that? Actually I know they have a better one, because licensing.support@mitel.com uses OTRS.
My experience with MiVB support in the UK isn't great. Take their sweet time and you'll eventually get a patronising response, responses indicate they obviously haven't read what you've put on the ticket, etc. Support for MiCC, on the other hand, is the opposite. Swift responses [get this - sometimes they even call you rather than emailing!] from someone who knows the product inside out, almost always fixes it first time and usually leaves me with a handy little tip or trick for managing MiCC into the bargain.