Adding Galaxy Nexus as second line, then switching

[guzzy2792]

I have a Droid Inc. 2 with no upgrade till 2013. Now I was going to add another line for another member when i got this idea.

Can I buy a Galaxy Nexus on my new line. Give it the plan I want to give the other family member, then when I get the phone activate the Nexus on the 1st line, and give the Inc 2 on the second line. The 2nd line was for my mom with an iPhone, but I would give her my iPhone then once the switch is complete, switch out the Inc 2 with the iPhone 4