The MNE101170 ECU is a coded Cooper unit and would 'originaly' have only been fitted to 95 onwards Coopers, the non Coopers still had the alarm wiring but the alarm itself was an option, where there is no alarm, there is a black box that looks almost the same as the alarm ECu, but all it really is is a junction box for the alarm and imobiliser wiring. These cars ALL have the wiring in the body loom for the alarm. Earlier Cooper models had an alarm that was again part of the body loom, but lacked the coding and it did not need to talk to the engine ECU.
Either the car this ecu came from has an alarm and imobiliser, or the ecu has been de coded and installed as a replacement and some one has cleverly removed all traces of the alarm wiring from the loom, which pretty much means the loom has to be taken appart at the seams.
By all means try the ecu, if it works, great, if it doesnt, it is because it is a coded unit and is not recieveing the digital code signal from the alarm ECU.