I've seen Maria Stuarda at least four times - way back at the 1969 Edinburgh Festival with Leyla Gencer (aargh!) as Maria and Shirley Verrett (hurray!) as Elisabetta. Then in the early 70s at the Coliseum (in English, of course) wth Janet Baker as Mary and Pauline Tinsley as Elisabeth (conducted by Charles Mackerras), and the same production in Bradford with Tinsley again and Sarah ("I'm tone-deaf") Walker. Long gap, when I could have seen it at Buxton in the '90s, and most recently performed by Opera North in 2010 with Sarah Connolly as Maria (back to Italian) and Antonia Cifrone as a whipcracking Elisabetta.

I don't know why the Met has never done it before - maybe the Beverley Sills effect?

Anyway, on the subject of the confrontation of the queens, here it goes in English (translator: Tom Hammond):

Mary: You'd insult me, foul-mouthed usurper?
All: What presumption! Lady, be careful!
Elisabeth: Silence! Silence!
Mary: Ah no! Shameless daughter of a harlot!
Talbot (aside): Heaven help her!
Mary: How dare you speak of dishonour?
You licentious, painted creature,
How I blush for your behaviour!
You've dishonoured the throne of England,
Royal bastard, all these years!

Incidentally, George Talbot, the 6th Earl of Shrewsbury, sometimes reveals himself to Mary as a Roman Catholic priest at the end of the opera (enraging the Italian censors in the 1830s). Apparently this was Bardari (the librettist)'s invention, in which Talbot and young Mortimer in Schiller's play were conflated, so that's another difference from the real historical events. Talbot, of course, was a real person and was Mary's principal keeper (she was moved around England quite a bit) in between her capture and execution.