It is often required to be able to look at all your subscriptions and how they're all tangled together with subscribers and channels, especially when you've inherited a SCOM management Group from someone else and you're trying to explore the environment. It is very tedious to map together all the subscriptions manually and and it takes a lot of time as well.
Having faced with a similar situation recently, I wrote this quick initial version of a script that will fetch all these relationships for you and export them to a text file under "C:\Temp\subscriptioninfo.txt"
Just rename the file as .ps1 and run it as an administrator. I will try to further release modified versions of the script to make it "cleaner" and "optimized".
Hope this helps!