Answer: Joseph. You are referring to a concept called "eminent domain" -- also known as "condemnation". The short answer: if the taking of the property is for a "public use" -- such as road or a rail transit -- the government has the absolute right to take your house or even your business.
The Fifth Amendment to our Constitution reads, in part: "nor shall private property be taken for public use, without just compensation". And the Fourteenth Amendment applies that same concept to all States. That means that while you have very little chance to fight the taking, you can challenge the amount the government initially offers you. You have the right to a full jury trial to have the court determine what is "just compensation".
Although the process may differ from state to state, typically once the government makes a determination that it needs certain property for its "public use", it may actually hold hearings where the pros and cons are discussed. In fact, often you -- the effective homeowner -- may not even be aware of the facts until you get a formal notice of the taking. In many states, the government does what is known as a "quick take" -- they immediately record the title to the property in the name of the government.
What is a public use? A 2005 Supreme Court opinion muddied the waters somewhat when it ruled that the City of New London, Connecticut, could condemn private property and give it to a private developer to be used a part of a comprehensive redevelopment plan. According to the Court, "the governmental taking of property from one private owner to give to another in furtherance of economic development constitutes a permissible ‘public use' under the Fifth Amendment." Kelo v City of New London.
As a result, many States have reacted to the high court's decision by enacting legislation that prohibits a state from taking property and giving it to another private land owner, even for example in the case of job creation.
I suggest that you and your neighbors immediately retain experienced local counsel so that you will be prepared in case that condemnation notice comes your way. There should be a lot of advanced preparation, such as getting your own appraiser, so that you will be able to challenge -- if necessary -- the dollar amount that the government will initially offer you as compensation.