Not switchable to my knowledge, but the HD/SDI output does have a 4:2:2 color compression, which is better for green screen than the 4:0:0 of the SxS cards if you use a Convergent Design method of capture. <http://www.convergent-design.com/>
[Jim McNally]"When I have my EX3 setup in 1080/30p mode the YPbPr/SDI out is showing 1080/60i. "
On my EX3 in the VIDEO SET menu the YPbPr/SDI Out Select can only be set to HD or SD. Jim are you talking about seeing the 1080/60i description somewhere on the EX3 or on the MXO? Because if it's the MXO then you just need to make sure that end of it is set up for 1080//30p. Even if you can't change that I'm pretty sure it will still be recorded as 1080/30p and not 60i. Try recording a couple seconds and bring the result into your NLE. Check the field order description and that it says "none".
For Greg: As Craig has stated the SxS cards record in the 4:2:0 colour space. There's a pretty big difference between 4:2:0 and 4:0:0. Personally, I'm waiting to win the lottery so I can get my F35 that records in the 4:4:4 colour space.
The EX-1/3 records Progressive as PSF (Progressive Segmented frame).
Its write it as an Interlaced file.
Also the HDSI out put Progressive in an Interlaced fashion.
This allows you to monitor in an interlaced screen.
Don't worry, what you get recorded is progressive.