Hewlett Packard, one of the biggest tech industries around the world, used for around 1 year the same audio-conferencing solution I had developed for Itaú bank.
They used the product internally by their technical staff to solve technical issues by phone.
Since the audio-conferencing solution provided the ability to create several IVRs (Interactive Voice Response) flows, each IVR flow provided a channel to a specialized PSTN support channel.
The solution was developed around 2006 using a mix of languages (mainly C++/Qt) and PostgreSQL database. Since it had to accept PSTN calls, all servers used a specialized card developed by Khomp (http://www.khomp.com/en/)
More info about HP at http://www.hp.com/