LT = 'local technique', as in your previous question; soemtimes this is just an 'electrical cupboard', but by the sound of it, this must be somewhere larger, so 'plant room' ought to do the trick.

GE very often = 'groupe électrogène', so 'generating set' or 'generator' — you should very easily be able to confirm this from your wider context, as there is surely bound to be some other mention elsewhere of a generator or emergency back-up power supply?

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Note added at 2 hrs (2018-07-25 09:11:50 GMT)
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In EN, a 'plant room' is a special area, usually with a more 'utilitarian' finish (and certainly not intended to be visietd by the general public!) intended for housing 'plant' — i.e. any kind of technical equipment (which may or may not be electrical in nature)

This is a generic term and can refer to room-spaces of many sizes; what makes it a 'room' rather than a 'cupboard' is in essence simply whether or not you can physically walk into it. It can be used for HVAC plant, boilers, swimming-pool plant, emergency generators, computer or telecoms interconnections, etc. Hence its usefulness as a catch-all term if it is not possible or desirable to be more specific.