Edit: Apparently this question was marked 'popular', so I thought I would mention that I found my solution, which has worked without issue: An app called DisableService which let me disable the Motorola OTA Update service. Root is required.
I've been trying to avoid my phone updating for about a week now. Every few minutes I'm switched away from whatever app I'm using to an update screen. Originally there was an option to update later, but now it's gone and I simply switch back to the app I was using. Obviously, this is quite disruptive. Unfortunately, I tapped the 'Okay' (something to that effect) button and now it's attempting to download the update in the background. I've been able to mitigate this by stopping the MotorolaOTA app, and disabling Wi-Fi.
I'll be clearing out all my Wi-Fi connections in case my phone connects to one and continues the update. I'll also see if I can introduce something which blocks the update servers.
How can I cancel this so I don't have to worry about the update completing? I have compatibility concerns.
How else can I battle this OTA terror? Please, you're my only hope!
I have a Motorola Moto G, XT1031.
Edit: I have multiple ideas. One is to, and I don't yet have extensive knowledge of how SSL certificate authorities work, but to introduce a custom root CA, with a CRL including the update server.
Cruder methods include: running a nameserver to use when on Wi-Fi, which blocks the update server, or a proxy/VPN which could filter requests. Maybe I could create a fake update server which says, "all good, no updates" and make my phone talk to it with a custom root CA certificate.