Employees need to get over it, and understand that a second line is a blessing.
I work as a Corporate Store Manager for Bell in Canada, and 90% of my peers carry a single device, and use the same device for work and personal. Bell supplies the line, and they bully vendors into supplying the hardware. Of the 40 or so managers in town, and several hundred sales reps, every single one of use that has been around for longer than 3 months (policy change) carries a Bell supplied line.
I carry my Bell supplied line (BB z10), as well as a personal line (Galaxy Note 2) daily when I am at work, although I tend to leave the Note in my jacket pocket, in the stock room. None of my peers, none of my staff, and none of my superiors have my personal line number, outside of HR, in my employee file.
Conversely, I leave the z10 in the same jacket pocket when I am home, or out and not working.
Work / Life balance is far more important to me than a little bit of extra weight in a pocket.