Well, getemed AG is probably not amoung those five monitor producers you mentioned, but anyhow:
Data formats and file formats are not that easy to define; there's a lot to account for. Data must be handled by embedded systems, must be transferred via small-bandwidth connections, must be quickly decodable, must be streamable and must be backward compatible, just to mention a few requirements.
We here at getemed have a well-defined file format that fullfills all those and some more requirements and is not published. But if any of our customers asks for a transverter and gives a good reason he is given a transcoder that exports getemed data streams to text (csv) or xml files.
Any 'simple' binary or ascii data format we have checked had collided with one or more of our requirements. This data format is documented and we have given the format out to a few of our costumers as well, but it is also still 'alive', so might change from time to time (while being backwards compatible as required; meaning older versions of processing SW can handle all those parts of a data file that's definition is still valid, can use a compatible way of handling newer data components that are similar to older ones and can safely ignore other parts of the data).
Just my € 0.02
