The agreement itself will have the necessary details as to when and how the bond can be demanded. If the agreement allows a proviso then that too needs to be considered. it is important that you let them know with a proper letter invoking such proviso in the agreement if any is available to you.

In case they decide to challenge you and demand the money they have to do so through court and that will anyway take them lot of time and effort which i do not think they will be willing to do. If however they do not release any document of yours then you yourself can file a writ against them and demand your documents bank. you are lucky to have such remedy available considering the company is a PSU.

There is no circular in this regard.