I found this in the BLHeli documentation - the left hand picture looks like a match for the picture Ocracoke posted earlier in the thread. This is the same ESC by the looks of it, just the 45A version.

Screen Shot 2018-04-07 at 15.34.51.jpg

Following that trail I then found this for the underside of the 65A variant, for those not brave enough to take one apart:

Turnigy AE-65A_2.JPG

Conclusion: it's SiLabs MCU based, and ultimately that means no use of the existing TZ85A Brushless firmware or SimonK, both of which are only Atmel AVR MCU compatible