TransactionScope automatically escalating to MSDTC on some machines?

In our project we're using TransactionScope's to ensure our data access layer performs it's actions in a transaction. We're aiming to not require the MSDTC service to be enabled on our end-user's machines.

Trouble is, on half of our developers machines, we can run with MSDTC disabled. The other half must have it enabled or they get the "MSDTC on [SERVER] is unavailable" error message.

It's really got me scratching my head and has me seriously considering rolling back to a home-spun TransactionScope-like solution based on ADO.NET transaction objects. It's seemingly insane - the same code that works (and does not escalate) on half of our developer's does escalate on the other developer's.

I was hoping for a better answer to Trace why a transaction is escalated to DTC but unfortunately it doesn't.

Here's a sample bit of code that will cause the trouble, on the machines that try to escalate, it tries to escalate on the second connection.Open() (and yes, there is no other connection open at the time.)

using (TransactionScope transactionScope = new TransactionScope() {
   using (SqlConnection connection = new SqlConnection(_ConStr)) {
      using (SqlCommand command = connection.CreateCommand()) {
         // prep the command
         connection.Open();
         using (SqlDataReader reader = command.ExecuteReader()) {
            // use the reader
            connection.Close();
         }
      }
   }

   // Do other stuff here that may or may not involve enlisting 
   // in the ambient transaction

   using (SqlConnection connection = new SqlConnection(_ConStr)) {
      using (SqlCommand command = connection.CreateCommand()) {
         // prep the command
         connection.Open();  // Throws "MSDTC on [SERVER] is unavailable" on some...

         // gets here on only half of the developer machines.
      }
      connection