I do not, nor have I ever, used my personal cell phone for work purposes. Key work people may have the number for emergency purposes, but it's made clear that me providing that number is a serious point of trust, and that it should never be used except for the most dire circumstances. My work cell not answering doesn't count. Clients are to *never* get that number.
About a year ago, I took a job where they don't provide a phone. I chose instead to purchase a separate line that is used entirely for business. Only a few personal contacts have the number (parents and wife, basically). If I ever leave the company, the line gets disabled (phone was purchased off contract) so I don't have to field calls from clients. Even if I choose to use the phone with a new employer, it will get a different number. The cost of the phone and extra line comes off taxes each year.
When traveling internationally, the phone gets backed up, wiped, and reinitialized with a separate ID that has no links to the old except for necessary work contacts. Something similar happens to the notebook. After returning home, what little new data is present is backed up, then the pre-trip backups are restored.
All devices are fully encrypted, so reinitialization gets a fully clean start.