In my experience when the ICF was actually submitted (with all the data that was requested), the ICF was approved the next day. And from there it was 30 days for a check to appear.
However, the ICF itself was a multi-step process to get submitted properly. I needed AESC to send someone to my house to take pictures of the Powerwalls and test them to see if they worked. I needed Tesla to produce data to SGIP so they knew the batteries were discharging. I needed to allow a PG&E person to throw the disconnects and test the backup was working. I don't know what fraud was happening with SGIP, but they triple-check everything to see if the Powerwalls are real and functional.
PS. buy one of these to frame the check if you ever receive it...