On average what amount and/or percentage does your company contribute or reimburse for cell phones? Does anyone have an expense policy template they are willing to share?

This has been answered, it all depends on what YOU want. From a fix $ amount per month to only for specified international calls to pre-approved numbers, etc.

It comes down to a) does the employee use their phone for business because you want them to or for their convenience, b) do you require the employee to make themselves available by either phone/email/text or c) it's just a perk?

Cell phones like any other T & E type expense can be abused. As such, either a flat rate or build in a monitoring facility to make sure bills don't get abusive.