Q:

Did British officers in Egypt use Indian soldiers to translate all radio messages into Hindustani? 

I'm not entirely sure how notable this claim is.  But a popular Tweeter named WW2 Tweets from 1941 made the following claim:

British officers in Egypt now using their Indian soldiers to translate all radio messages into Hindustani- fearful of snooping Germans. 

The tweet was retweeted 68 times and favourited 26 times.  It has (since) been doing the rounds in blogs and such. 
Is there any basis for this claim? 
(One of the repliers to the tweet claims that the Indian army similarly employed Tamil during the 1971 Bangladesh/East Pakistan War.  A less notable claim, but just as interesting.) 

A:

Did British officers in Egypt use Indian soldiers to translate all radio messages into Hindustani? 

No, certainly not all. 
All radio messages includes both voice messages and morse-code messages. 

At least some messages were enciphered using a different system.  See British Army Low Grade ciphers used in World War II
At least some radio messages were intended to be received by the Germans for purposes of misinformation.  See El Alamein

And certainly not all messages in Hindustani would have required required an indian soldier. 

As compro1 notes in a comment, In at least one case, the services of an Indian soldier were not needed.  General Frank Messervy was born in Trinidad to English and French parents.   - Unless the term "Indian soldier" encompasses all the soldiers of every nationality who ever served in the British Indian army.