The function of the private line eliminates the possibility of someone other than you reviewing your call details, from phone sets, which have the shared extension, additionally no one can monitor your call or connect to you call.
Hosted PBX service provider in Canada.
http://pbx.tieus.com
Only $16.95/mo, unlimited calling to 20 major Canada Cities.
unlimited calling for your cell phone
http://www.magicnumber.ca