I would get some specifics.
1. I haven't heard of a 16 wire (eight-pair) cable.
2. What is the wire rated for network data transmission? Cat5 UTP (or higher) is the recognized standard for network cabling. Ask the installers if they will guarentee that the cabling will meet the IEEE 802.3 standard specification for network cabling. If they give you a blank look, move on to another vendor.
3. You would need to run a big cable to every location where you need either a phone or a computer, regardless of whether both coexist in the same location.
4. Bigger cable is harder to handle (takes more time to run) and probably costs more to install.
5. If one cable is cut, you lose both phone and data.
6. Network cable closets and phone closets aren't always colocated.
One possibility:
I have seen some new hybrid cables that can bundle phone, network, TV cable, and sound wiring in one bundle. However, these hybrids are mainly designed for the high-end home market. The cable being pushed by the vendor may be one of these hybrids. Again get specifics, especially regarding standards.
