<?xml version="1.0" encoding="UTF-8"?>
<transcript>
<text start="23.49" dur="5.97">
  &amp;gt;&amp;gt;Commentator: We have here today, Steve with
  us whom I met not too long ago at something
</text>
...
</transcript>

using System;
using System.Linq;
using System.Text;
using System.Web;
using System.Xml.Linq;

namespace YtSubs
{
  public class GoogleXmlToSrt
  {
      public string ConvertXmlToSrt(string url)
      {
          var transcript = loadTranscript(url);

          var srtBuf = new StringBuilder();
          var lineNumber = 0;

          foreach (var item in transcript.Root.Elements("text"))
          {
              lineNumber++;
              srtBuf.Append(lineNumber.ToString());

              var timeLine = getTimeLine(item);
              srtBuf.AppendFormat("{0}{1} --> {2}{3}", Environment.NewLine, timeLine.Item1, timeLine.Item2, Environment.NewLine);

              var msg = decodeText(item);
              srtBuf.AppendLine(msg + Environment.NewLine);
          }
          return srtBuf.ToString();
      }

      private static XDocument loadTranscript(string url)
      {
          var transcript = XDocument.Load(url);

          if (transcript.Root == null)
              throw new InvalidOperationException("couldn't load received data.");
          return transcript;
      }

      private static string decodeText(XElement text)
      {
          var textValue = text.Value.Split('\n');
          var msg = textValue.Aggregate(
                  string.Empty, (current, line) =>
                  current + (HttpUtility.HtmlDecode(line.Trim()) + Environment.NewLine)
                  );
          return msg.Trim();
      }

      private static int fractionalPart(string data)
      {
          var idx = data.IndexOf(".");
          if (idx == -1) return 0;
          var fractionalPart = data.Substring(idx + 1);
          if (fractionalPart.Length == 1) //3.4 --> 3.400
              return int.Parse(fractionalPart + "00");

          if (fractionalPart.Length == 2) //3.04 --> 3.040
              return int.Parse(fractionalPart + "0");

          return int.Parse(fractionalPart.Substring(0, 3));
      }

      private Tuple<string, string> getTimeLine(XElement text)
      {
          var startTs = getStartTs(text);
          TimeSpan endTs = getEndTs(text, startTs);
          return new Tuple<string, string>(timeSpanToString(startTs), timeSpanToString(endTs));
      }

      private static TimeSpan getStartTs(XElement text)
      {
          var startData = text.Attribute("start");
          if (startData == null)
              throw new InvalidOperationException("This is not a valid subtitle file.");

          var start = startData.Value;
          var startTs = new TimeSpan(0, 0, 0, (int)Math.Truncate(double.Parse(start)), fractionalPart(start));
          return startTs;
      }

      private static TimeSpan getEndTs(XElement text, TimeSpan startTs)
      {
          TimeSpan endTs;
          var durData = text.Attribute("dur");
          if (durData == null)
          {
              endTs = startTs + new TimeSpan(0, 0, 0, 3, 0);
          }
          else
          {
              var dur = durData.Value;
              var durTs = new TimeSpan(0, 0, 0, (int)Math.Truncate(double.Parse(dur)), fractionalPart(dur));
              endTs = startTs + durTs;
          }
          return endTs;
      }

      private static string timeSpanToString(TimeSpan lineTs)
      {
          return string.Format("{0}:{1}:{2},{3}",
                      lineTs.Hours.ToString("D2"),
                      lineTs.Minutes.ToString("D2"),
                      lineTs.Seconds.ToString("D2"),
                      lineTs.Milliseconds.ToString("D3"));
      }
  }
}

using System.IO;

namespace YtSubs
{
  class Program
  {
      static void Main(string[] args)
      {
          var url = "http://video.google.com/timedtext?hl=en&v=-PA-buwI3q4&lang=en";
          //var url = "subtitle.xml";
          var srtBuf = new GoogleXmlToSrt().ConvertXmlToSrt(url);
          File.WriteAllText("-PA-buwI3q4.srt", srtBuf);
      }
  }
}