I'm not a huge fan of tribute bands, but in the past I have done plenty of YouTube surfing in the hope of finding that elusive ABBA vocal sound. My favourite A&F is Abba Chique, who unfortunately tend to limit themselves to local gigs in the South of England (I have no connection with them and have never even seen them live). The main thing about them is that they aren't just two generically competent singers turning their hand to ABBA: 'Agnetha' has Agnetha's vocal punch and 'Frida' has Frida's warmth.
Anyway, I've just come across a video of their recent live performance of Tiger. The following YouTube link skips straight to the final bars: check out the ending. 'Agnetha' not only hits the climactic high notes on 'Ti-ger' but then, just to show that this is nothing to her, she repeats the feat, this time raising the already challenging notes another half an octave. These notes (A5 on the 'Ti-' and G5 on the '-ger') are actually higher than the real Agnetha ever sang, with the exception of her B5 in HIYS.
Although she makes the 'Ti-' A5, the really impressive note is the '-ger' G5, which is sustained and powerful with vibrato. Fully committed, and way beyond the call of duty for a tribute act. Fair play to her!