when i first read this i thought fold. simple. whats this post about?
after thinking it through i think either a call or fold is ok. (use a randomizer?)

things to consider:
is UTG1 pouncing on a weak lead by BB with ATC?
UTG1: 24/18 694 hands so its not like he is spewing off chips.
his bet is less than 75% pot even after he's raised BB lead
why did he not cbet the flop?
so many bad/scare cards on river
position

with a bet and a raise in front of you it looks like your opponents are strong. however upon closer inspection UTG1 may be bluffing/semi-bluffing a very weak lead by BB. if he had a really strong hand wouldn't he bet closer to pot against two opponents? on the other hand his stats are sensible and he's UTG1 and perhaps BB is trying to induce?

arguments can be made for either calling or folding... i'm probably leaning towards calling (just) and possibly cbetting the flop... i might even find a turn bluff raise on occasion if I really think he;s attacking the BB's 12.5% pot size bet on turn.

why didn't you bet flop ip? (not saying you should have necessarily)

Interesting spot indeed. I really can't see we could bluff that turn w/ AhJh, if the Ace was spades/diamond we could do it? Still dont like to do it in multiway pot. Also I think utg1 range hit that board quite hard + so many bad/scare cards on river like impregnatio said. We have risked a bit over 2bb so far. I would let it go. well played imo. arguments?

betting flop ip is something we could do like said.

BB lead turn looks to me very weak
UTG1 range looks to me like QTs,JJ,AJ,QJs,TJs,J9s,QQ,spades maybe but i block a lot of these

About bet flop vs missed cbet 3way IP. I just don't think i take the pot often enough to bet here. BB could have many Kx 9x FDs etc and initial raiser also could have x/c range here with second pairs QQ TT A9s etc. I don't know maybe it's profitable but i would be more inclined to bet this with heart OTF.