I had the same exact issue when I upgraded to El Capitan on my 13 inch MacBook pro and did the following to get my MacBook Air Superdrive to work in El Capitan...
*** You first need to disable SIP in El Capitan otherwise you won't be able to do the following steps. ***
**** I first followed this guide to add the "mbasd=1" into the com.apple.Boot.plist file. Here is the link I followed:
http://www.hardturm.ch/luz/2011/10/how-to-make-the-macbook-air-superdrive-work-with-any-mac/
**** I then ran into an issue with my DVD Player and had an initialization error [-70012] so I researched further and found this thread:
http://macenstein.com/default/2011/07/how-to-get-your-external-super-drive-working-in-lion/
Following the procedures outlined by both threads, I was able to fully restore the functionality of using my MacBook Air Superdrive on my MacBook Pro.
Initially when I tried using my DVD Player after performing the first procedure, I ran into a glitch in El Capitan and got a
DVD Initialization error [-70012] and couldn't play any DVDs which led me to the second link above...
To correct the DVD Player Initialization error the second procedure has you using a hex editor. Follow the procedure to the letter because when you make changes using the hex editor, you can cause damage to the file so having a backup of the "DVDPlayback" file is highly recommended. I used 0xed hex editor which I found to be much easier to use than HexEdit.
http://www.suavetech.com/0xed/0xed.html
1) When using the Hex Editor (from the procedure mentioned above), you end up navigating to
System -> Library -> Frameworks -> DVDPlayback.framework -> Versions -> A
2) copy the
DVDPlayback file inside the folder labeled "A" and make a backup. Rename the file
DVDPlayback.bak or something like that. I also looked at the permissions to this file and enabled read & write for everyone so that I could modify this file.
3) Then just follow the procedure outlined in the second link I provided above and you should be good to go.
Hope this helps you guys/gals