This is a sensitive subject. I understand that it's hard for Germans to let go of hard-earned titles like 'Dipl. Ing.' (And not just Germans -- Latin Americans as well, and others too for all I know.) But the thing is, in English such titles really, truly *are not used* except on résumés. Not as titles, and definitely not as forms of address.
Anyone who has a job as an engineer is simply assumed to have the relevant degree in engineering. So making a point of citing an academic title within a normal piece of text (as opposed to, say, at the top of a journal article, when the author's degree(s) might indeed be listed, once) only looks like boasting, or insecurity, or both. And perhaps *especially* in engineering. The engineers I know are the first to say that they rarely use at work what they learned at university anyway; the knowledge in their field simply changes too fast.
But if your company absolutly can't resist dropping a hint that its engineer is not just some guy who walked in off the street, IMO you can only do it by slipping in a phrase like 'Mr. X, an engineer with Y firm.' That is: I agree that 'Mr. Engineer' and 'Mr. Dipl. Ing.' and even 'Mr. X, Dipl. Ing.' are simply not thinkable in English.
Neither, by the way, is 'Mr. General.' Please, O ye LEO gods, tell me that 'Sarah' is not another RV-outbreak. But judging from 'my spouse' alone, not to mention the other telltale signs, it certainly looks like it.
Here's a thought (to try to keep this vaguely on topic): Maybe RV's 'spouse' is in fact a gay man, since the gender-neutral term 'spouse' is normally used only in writing, not in conversation by people who *know* which gender they're married to. (Although come to think of it, there was that movie 'M. Butterfly.' Hmm. Ah, the joys of 'Don't ask, don't tell'...) Perhaps RV, if this is he, just hasn't yet heard of 'partner' or 'companion.'
Or 'ma'am,' for that matter. ('Madam'?! Geez...) ;)