Sysadmin-types, we kind of have to have a phone. It's what the monitoring system makes vibrate when our attention is needed, and we also tend to be "always on-call", even if it's tier 4 emergency last resort on-call. But sometimes we're the kind of on-call where we have to pay attention any time an alert comes in, regardless of hour, and that's when things get real.
So what if you're in that kind of job, or applying for one, and it turns out that your employer doesn't provide a cell phone and doesn't provide reimbursement. Some Bring Your Own Device policies are written this way. Or maybe your employer moves to a BYOD policy and the company paid telecoms are going away.
Can they do that?
Yes they can, but.
As with all labor laws, the rules vary based on where you are in the world. However, in August 2014 (a month and a half ago!) Schwann's Home Services, Inc lost an appeal in California Appellate court. This is important because California contains Silicon Valley and what happens there tends to percolate out to the rest of the tech industry. This ruling held that employees who do company business on personal phones are entitled to reimbursement.
The ruling didn't provide a legal framework for how much reimbursement is required, just that some is.
This thing is so new that the ripples haven't been felt everywhere yet. No-reimbursement policies are not legal, that much is clear, but beyond that, not much is. For non-California based companies such as those in tech hot-spots like Seattle, New York, or the DC area this is merely a warning that the legal basis for such no-reimbursement policies is not firm. As the California-based companies revise policies in light of this ruling, accepted-practice in the tech field will shift without legal action elsewhere.
My legal google-fu is too weak to tell if this thing can be appealed to the state Supreme Court, though it looks like it might have already toured through there.
Until then...
I strongly recommend against using your personal phone for both work and private. Having two phones, even phones you pay for, provides an affirmative separation between your work identity subject to corporate policies and liability, and your private identity. This is more expensive than just getting an unlimited voice/text plan with lots of data and dual-homing, but you face fewer risks to yourself that way. No-reimbursement BYOD policies are unfair to tech-workers the way that employers that require a uniform to be worn who don't provide a uniform allowance are unfair; for some of us, that phone is essential to our ability to do our jobs and should be expensed to the employer. Laws and precedent always take a while to catch up to business reality, and BYOD is getting caught up.