That pesky plus signs and mobile phones [telecom]

At home we have AT&T and recently had T-Mobile for our cell service. I noticed on all phones, regardless of manufacturer, incoming SMS and calls without names assigned displayed in the +1xxxyyyzzzz format. Specifically the number is prefaced with the +1.

I have a Verizon phone at work. I only see xxx-yyy-zzzz. What's more, I cannot call internationally by using the (+). The phone doesn't recognize that. I have to use 011. My attempt to call

+60-4-yyy-zzzz resulted in a call to Vancouver.

Is this difference due to GSM versus CDMA?