From some quick testing: One can import a Word document with embedded MS Word equation objects into Google docs, but the equation objects do not come through very well.
One can also create separate equation objects in Google Docs, online as seen in this google doc version of Korteweg – de Vries Equation but I found the editor palettes in Google Docs very clunky. Additionally the document can be saved back to Word format, and the equation comes through, but only as a low res image.