If you are buying a property via Atlas in general they are acting as agents and it will be the builders who provide the bank guarantee
These are only provided for off plan which in this recession may not be the best approach to buying in Spain unless it is very good
But in the main, off plan developemnts have been mothballed ,because the developers can not get enough sales to enable them to raise the finance
Also the banks will not be too keen to give guarantees just now!...but if that is what you want to do ,then make sure you get your BG 'at the same time' as you hand over the money
I do act for a small developer who only builds villas to order and he gives a BG because it takes on average circa 1 year to build and get the licence of first occupation...this is not really off plan as we have known it in the past ...and he has no problem getting his bank to give a BG
Just now there is a very large choice of ready now and re sales plus distressed sales and you can get a very good buy ....and you can see what you get..........very few are buying off plan...if any except for the example above
So perhaps you should re consider your approach to buying in Spain.......I'm surprised that Atlas are still trying to sell off plan!