As of 2010, other word processing programs can’t open a Pages file. However, Pages also embeds a PDF file in each document. PCs and Mac computers don’t need iWork to open the PDF file and access the text of a Pages document.
The site linked above has a few steps to access a pdf version of a pages doc if you don’t have Pages. Basically change the extension to zip, unzip it and there’s a pdf in the QuickLook dir. So great!