At most companies I have worked with recently the telephony guys were the same team as the networking team. Especially since most companies have/are planning to migrate to some sort of VoIP system. That certainly seems to be the trend going forward.
Generally speaking, I have found that MOST of the time the networking teams at larger enterprises are pretty reliable. They usually do a pretty good job of getting configurations right when asked, etc. Unfortunately, troubleshooting the network is typically an important step in diagnosing an issue, and often times you aren't able to properly diagnose an issue unless you can get a packet capture, etc. This leads to the network teams spending a great deal of time helping other people troubleshoot issues that "aren't their problem." That can be very frustrating, and if the network team spends a lot of time doing this then it can impact their ability to get their other work done.
I try to keep this in mind when dealing with network teams (and really any other team outside of my own) and try to minimize my impact. I'll double and triple-check my designs and make sure that they are in as clear and concise format as possible before handing them off to the network team to implement. Likewise, I double and triple check my troubleshooting before asking them to get involved in the process. Rather than asking "is that port on the correct VLAN" or "is it configured for trunking rather than switchport access" I tend to approach it as "I'm having an issue with X on such-and-such port. I'm seeing Y. Can you tell me what you're seeing?" Then instead of coming across as accusing them of making a mistake I sound much more neutral.
Really you should probably be doing this with any external teams or organizations that you're dealing with. Soft skills can go a long way.
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