Hello, Victorycountry, on strike, on honeymoon are grammatical collocations and, if questions arise, they can be resolved in any quality general dictionary or a more specialised combinatory dictionary. They use of on lunch is open to objection as at lunch is virtually the only option with a preposition. Your assumption about prepositional phrase-progressive aspect correlation seems promising, but, in order for it to become a rule it should embrace a certain number of cases.
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