How to convert video shot in 60fps into 24fps in final cut express?

FCE doesn't support either 60fps or 24 fps, so I guess the answer to that question would be no.

Not in FCE.

Since FCE only supports frame rates of 50i, 25p, 60i, and 30p, you won't be able to find a plugin that will extend its functionality in this respect.

FCS and After Effects would both be able to do the task you are looking for.

You can edit in 25fps in FCE and use this python script to conform 60fps to 25fps:
http://www.cinema5d.com/viewtopic.php?f=13&t=4490

So, when I look at item properties for video shot in 720p60 and it shows the 59.94fps it is interlaced, not progressive?

No, why would you say that?

Because saklicki (or whatever) stated:

"Since FCE only supports frame rates of 50i, 25p, 60i, and 30p, you won't be able to find a plugin that will extend its functionality in this respect."

That leads me to believe that a 720p60 file would only be used at 720i60 since it does not support 60p...

There is no 720i60. All 720 media is progressive, either 720p30 or 720p60.

OK - so then is what was stated (and quoted) earlier correct or incorrect. Either FCE works with the 720p60 that I am shooting which makes the above statement incorrect OR it is transcoding or handling it in some other way to make it 720p30 or somehow interlacing it - which makes it right. Which is it? Anyone?

What you quoted says nothing about 720. There are other HD formats besides 720. All the information is available on the Internet. Most of it in Wikipedia.

ok so what you are saying is it does support 60 fps then? I know the post says nothing about 720, it states that FCE doesn't support 60p so whether it is 720, 480 or whatever home made concoction, it doesn't support it. The reason I stated 720p60 is because there is no broad supported standard in 1080p60 and I didn't want to be attacked for using an unsupported HD standard as an "example". Clearly you don't know the answer and are just avoiding it like any politician.

"ok so what you are saying is it does support 60 fps then?"

Where exactly do you claim I said that? FCE doesn't support other 60p material or 24p material. I don't know what you think you're trying to do, but it can't do it properly in this application.