Applicants through UCAS with the IB do have more time to formulate a clearing/adjustment strategy. And some universities enter into conversations with EU applicants (eg French bac, whose exam results are published in early July) well before A-level results are published.
Both statements are correct. However, for competitive courses for which very few places will be available in Clearing, no offer is usually made until A level results are out - such courses will want to take the very best applicants for their remaining few places.
For courses with a number of spaces in Clearing, it doesn't make any difference if Scottish or foreign applicants get a space earlier than A level students - there are far more of the latter anyhow. I think it is still normal to delay official offers until after A level results are out, but I'm not sure whether this is a strict rule.
Getting earlier choices of accommodation may be an issue for some universities, but increasingly universities do try to guarantee halls accommodation for all first years (firms, insurances and clearing).
Popple, I think they are under a legal obligation to treat all EU applicants equally.
This is true in principle. However, it is a very subtle issue given that the EU qualifications are not identical to the A level qualifications i.e. in practice you are automatically setting different entrance requirements anyhow.
BTW for postgraduate students we actually don't treat EU applicants equally - studentships pay fees only for EU students, but fees and maintenance for UK students. There is a pending case in the European court about this, although it is now a moot point given the imminent Brexit.