I have received many requests from Bosniaks in recent years, asking about their relatives who served in Austro-Hungarian army during the WWI. They wanted to know which units they served, what happened to them, where are they buried etc.
The only institution that might have information about Bosniaks in Austro-Hungarian army during the WWI, is Vienna's Kriegsarchiv. Please, contact them by phone, fax, mail or email and they can help you. Here are contact details:
Nottendorfer Gasse 2
They are very friendly and will definitely let you know if they have required information. For one hour of work / research they will charge you 35 EUR. Please, note this will be charged even in the case they don't find any information.
If you need additional help or advice, let me know.
Dr. Ahmed Pasic