Using the built in libraries for asp.net (System.Runtime.Serialization and System.ServiceModel.Web) you can get what you want pretty easily:
string[][] parsed = null;
var jsonStr = @"[[""Boston"",""142"",""JJK""],[""Miami"",""111"",""QLA""],[""Sacramento"",""042"",""PPT""]]";
using (var ms = new System.IO.MemoryStream(System.Text.Encoding.Default.GetBytes(jsonStr)))
{
    var serializer = new System.Runtime.Serialization.Json.DataContractJsonSerializer(typeof(string[][]));
    parsed = serializer.ReadObject(ms) as string[][];
}
A little more complex example (which was my original answer)
First make a dummy class to use for serialization. It just needs one member to hold the result which should be of type string[][].
[DataContract]
public class Result
{
    [DataMember(Name="d")]
    public string[][] d { get; set; }
}
Then it's as simple as wrapping your result up like so: { "d": /your results/ }. See below for an example:
Result parsed = null;
var jsonStr = @"[[""Boston"",""142"",""JJK""],[""Miami"",""111"",""QLA""],[""Sacramento"",""042"",""PPT""]]";
using (var ms = new MemoryStream(Encoding.Default.GetBytes(string.Format(@"{{ ""d"": {0} }}", jsonStr))))
{
    var serializer = new System.Runtime.Serialization.Json.DataContractJsonSerializer(typeof(Result));
    parsed = serializer.ReadObject(ms) as Result;
}