Generally speaking, to be able to be changed into passive, a verb must be transitive - it must have a 'doer', an action and a 'done to'. Usually, 'have' is intransitive - 'having' isn't really 'doing' anything, so there is no action and no 'done to'. So, it is impossible to change 'How many stations don't have electricity yet?' into passive.
Your sentences 1. and 3. are both active - they imagine the stations being able to 'be' electrified and 'have' electrified (all by themselves, with no-one doing the electrification). Your sentence 2. is passive, but it is not the equivalent to your original sentence. It is the short passive equivalent to 'How many stations have they electrified yet?'. The full passive equivalent is 'How many stations have been electrified by them yet?'.