As I started looking into this issue more closely, it seemed that the Atlantic Coast Conference (ACC) might be one in which all member teams have the conference logo (or in this case, wordmark) in their keys. After looking at several YouTube videos and doing screen captures, I can now document the big "ACC" letters in all the teams' keys...
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Whether it's a league policy that all schools feature the "ACC" in the key or just each school deciding independently to do so, I don't know. Most hardcore hoops fans will be able to recognize all the schools. For the record, though, they are (clockwise from upper right) Boston College, Duke, Maryland, Virginia Tech, NC State, Wake Forest, Florida State, North Carolina, Miami, Virginia, Georgia Tech, and Clemson.
Among other conferences, the Big East seems to have a lot of uniformity in the use of the conference wordmark in the key. The Big East has 16 teams. I have not checked all of their courts, but I've checked several and they all have the conference wordmark (here, here, and here).
If you know of other conferences that have complete uniformity on logos in the key, please share this information in the Comments section. If you could verify your assertion first by going to YouTube or other sites and viewing visual evidence from each court, that would be helpful.