After the MP3 file (Podcast) is downloaded it is then automatically transferred to iTunes. There is no streaming with Podcasts. Podcasting was created to get away from Streaming. Streaming - by definition is playing an audio / video file as it downloads from the net -- Podcasting is downloading the file in the back ground fully before transferring it to a program (usually iTunes) where it can be played at the leisure of the listener.
You can also listen to each episode without subscribing by playing it on-site using the play button.