To be blunt, information from a forum won't help you. The nature of the system and its security will depend on the government department, the nature of the contract, the intended purpose of the server, what the server needs to communicate with outside your own network, data protection legislation, and a multitude of other factors.
If you're serious about this, then your company needs project managers and some kind of customer liaison department to identify what the customer actually wants. Information on the requirements will be freely available to potential bidders *before* you secure the contract, since you need to know what you're bidding for (and whether or not you can deliver it).
