If the client is not using a firm to do all of their printing and is piece milling it out to different vendors, it is up to the client to provide the correct file. A good desgner provides the client with their logo in the acceptable formats needed to do print and web/electronic. I give at least 4 format logo variations to my clients with an explanation of how/when each are used. This included EPS needed for most print jobs and GIF needed for web (or PNG if they request it). I also provide a JPG file and a WMF. I also tell them there PMS colors for matching purposes.
Why provide all of this? Because it helps keep the logo consisitent in all areas of use. If the client places the JPG in their accoutning software, it will be the same logo as what he has printed on his signs, brochures and t-shirts that require an EPS format. Again, it is up to the client to ensure the correct file is provided if they are piece milling work out. If you stick with a firm, there shouldn`t be any conisistenecy issues.
I hope that helps shed some insight.