Can I still use the standard Eglu Go door handle with the Autodoor attached?

You cannot use both simultaneously. The casing for the mechanism that opens the Eglu Go Door sits on top of the T-handle that is used to manually open and close the Eglu Go Coop/Hutch, in a casing that fully encloses it. To be able to use the manual T-handle, you would have to unscrew the 4 screws that connect the casing to the coop/hutch and then lift the mechanism up to access the T-handle, you would have to re-palace this, fit the screws back, and likely re-calibrate for the automation to resume.