Two things. 1) Any MVNO I specifically namecheck as being a good option in the quick list of the Superguide can port over home phone numbers. 2) If you already have two cell phones and you're looking to keep your home phone number and service with it? More wireless service is not going to be your most cost effective solution, and you should probably switch over to a VoIP provider instead. Added benefit? You can either get a small little box that you can tie into the existing phone wiring in your house, but only if you can disconnect the phone line at the box outside your house (otherwise, you'll need a multi-handset cordless phone), or you can just forward incoming calls to either or both cell phone accounts. Again, the Superguide has the info and links you need.
I'm a big proponent of VoIP and a home phone line as a major savings option for families to save on their wireless bills, but you're both getting free service from work on that front, and if they're okay with you using work resources for personal calls, do so. Spork raises a good point, but also be mindful of who actually owns the cell phones and the phone numbers attached to them when it comes time for you to ever leave your job. Are the bills in your names and you're being compensated, or did they issue the things and pay the carrier directly? That should be something to consider with the whole discussion, as well.