TUPE is something of a minefield. Which is why private companies will frequently agree that it applies as a contract changes - doing that simply reduces the issues.
Of course those protected rights are usually lost within the first 18 months by a whole variety of means.
As for it applying in a transfer from the military to private sectors? My first thought is not a chance. The military do not have anything which resembles a contracted service. The hardware and personnel requirements are totally different - so the undertakings (that U in TUPE) are different....
Some of the early test cases revolved around whether equipment used in the undertaking of the contract was handed over - that might cover parts of the bases? Probably not though as a simple change in definition will make things look sufficiently different.
In short if yu are an office cleaner TUPE can protect your wages, if you are in a skilled profession - more skilled legal people will have ruled all of that out.....