If a VoIP line belonging to someone else in your team is on divert to you then any call for that person's line will not pop up on your screen, but instead will pop up on the person's screen that the line is associated with.

For example if Rachel puts her VoIP line on divert to her colleague Sarah then any call for Rachel will pop up on Rachel's screen when she is working inside the CRM but the call will ring on Sarah's phone as the line has been diverted over. 

If an incoming line is set to ring as a 'hunt group' ring - where all the phones in the hunt group ring in a sequence - your call pop up alert will not be displayed until your phone line rings as part of the hunt group.