Are admissions over the phone common?

[dudgeonmaster]

I noticed on Yuster that someone had been notified by phone that they had been admitted to a program I applied to. I haven't heard anything from them, and I was wondering if this most likely means I have been rejected. Are phone admissions only made on a case-by-case basis by professors who choose to call grad students who will be working with them next year, or is it standard practice for some departments to notify all accepted students (meaning I have been rejected)?