When using the minecart with TnT I sent it over the activator rail and after the explosion, the rails, and the blocks they were on did not get destroyed. This was in default superflat, and the rail were on dirt. the blocks around the rails were destroyed though.
Linked issues
Comments 2
Duplicate of MC-11544, please use the search function to see if your bug has already been submitted. Currently over 52% of tickets are being closed as duplicate.
I believe this is intended. Other information is shown on the wiki. http://www.minecraftwiki.net/wiki/Minecart_with_TNT