The Microsoft.SqlServer.TransactSql.ScriptDom.dll (part of the SDK) holds the Microsoft.SqlServer.TransactSql.ScriptDom namesspace,. Most every class in the namespace is marked Serializable. Here's the CreateViewStatement class, for instance: http://technet.microsoft.com/en-us/library/microsoft.sqlserver.transactsql.scriptdom.createviewstatement.aspx
However, the TSqlParserToken class is *not* marked Serializable. This means that, practically speaking, *nothing* is serializable, since almost every useful class has parser token members or properties. For instance, the TSqlFragment class has a ScriptTokenStream property (an IList of TSqlParserTokens) so it and anything deriving from it - any parsed result - is affected.