Some organizations consider taking the plunge off of big iron PBX platforms into IP telephony as being pretty daring, but that's nothing compared to what Sam Houston State University (SHSU) is doing. The south Texas school is boldly moving thousands of users off a Cisco VoIP platform to an open-source VoIP network based on Asterisk.
SHSU is in the process of moving its 6,000 students, faculty and staff off of Cisco CallManager IP PBXs and a legacy Nortel Meridian PBX over to Linux servers running Asterisk, which includes call processing, voicemail and PSTN gateway functionality. The driver for this project was cost, says Aaron Daniel, senior voice analyst at Sam Houston State University.
http://www.networkworld.com/news/2006/091206-von-sam-houston.html