You might be better emailing Andy about this as he is more in touch with the MTC people. They are wholesalers so may only deal with agents or distributors. I think if they did welcome the public then they would have at least said "by appointment".
There is plenty of good information on their website though including a link to photos on their Flickr page.
By the way, this was in one of the articles on the MTC site (first published in Northern Star newspaper in 2005) :
Mountain Top rarely supplies domestic outlets, but locals can try Mountain Top Coffee at Nimbinís Rainbow Cafe under the Cafiend brand.