>>>So could you dial 999 then when in Spain???
No. The European Conference of Postal and Telecommunications recommended in 1972 that 112 should be the standard emergency number across the whole of Europe. That decision was formalised by a decision of the EU Council in 1991.
999 can be used in a few (mainly non-European countries):
http://en.wikipedia.org/wiki/999_%28emergency_telephone_number%29
When I ran a railway station I needed to call the emergency services on many occasions. (Several fights, a couple of suspected fires, a stabbing, a suspected heart attack, various other medical emergencies, etc). I always used 112 as I tend to think of 999 as 'old-fashioned' and I still use 112 when, for example, reporting an emergency on a motorway. In 2009 the European Commission the European Commission and the Council of Europe signed a convention committing each to promote the 112 number on 'European 112 Day', which is on the 11th February each year. I have yet to see our Government doing much about it!