Another party could enter the fray, but it would still be difficult to get ARX. In the current deal, there is a $600M break fee, so right off the bat another party has to pay $600M more (ARX pays this, but for a buyer it means $600M less value). In addition, in the deal Shell has a first right of refusal to match any superior offer. So a third party could bid, and still not end up with ARX if Shell decides to match the offer. Because of this, a third party might have to make a much larger bid, in order to make it not worthwhile for Shell to match. While not impossible, these restrictions just make it less likely. In addiiton, Shell's market cap is $250B or so, much larger than most companies would might be interested in ARX. In terms of reasoning behind the deal, more information will be revealed when the offering circular is available.
5i Research Answer: