As hippy says, it's a little tricky to answer your question if the data can not be provided.
I2C is a synchronous method of serial comms and the timing limits should be in your data sheet - usually presented as numerical info plus a timing diagram (lots of wiggley lines).
Whether your transfer is at 50kHz or 100kHz it is usually neither here nor there. It's not like Asynch serial where timing is crucial because there is clock synch.
Best you get the I2C document from Phillips/NXP to show you about I2C definitions -
http://www.nxp.com/acrobat_download2/literature/9398/39340011.pdf
It doesn't matter whether its 24MHz or WhateverMHz , the I2C limit and spec should be provided in the Data Sheet as said by Martin.
The data transfer is governed by the clock rate limits which will be an arithmetical function of the master clock (and hardware/firmware limitations).
This, again, should be defined in the Manufacturer's Data Sheet.
If you have signed an NDA then it really is the responsibility of the manufacturers to provide you with the information rather than us lot guessing. And they will probably expect you to have a reasonable working knowledge of Synch serial comms.
The Manufacturer should be providing timing limitations (which reflect the maximum I2C speed which is what "slow" and "fast" really refer to). They should also provide you with address info and details on any other protocols and logic levels.
Sounds like a fun project. Let us know what happens.