I don't think it would be possible, but if you choose the splice MIL method, anything's possible if you don't know what you are doing.
The plug-n-play MIL elim's are the safest imo. The splicers work fine, too, if you know what you are doing.
Only thing I can think of is if someone tried to solder them in while they were still connected. Even then I doubt the wires could carry enough heat to hurt ECU.
my friend had a 96 gt and he put an x pipe in and didnt put the MIL eliminators in and sure enough the MIL came on with an O2 sensor code and the car ran like crap........so eventually he put in the eliminators and the light never came on but every once and a while the car ran the same as when the MIL light came on and the computer went into lean fuel trim mode.........
Think about what MIL eliminators do. They just send a modified amount of voltage to the ECM, telling it that converters are doing fine, which is the same thing the o2 sensors do without mil eliminators once you're in closed loop anyways. Unless you hook them up backwards (which I've done, and just threw a code,) you have zero to worry about.