I did a test this week of the nxcam and vegas 10.0 to sync by timecode.
First I connected to nxcams timecodes together, each in free run timecode. One set as input, one set as output. I connect an RCA cable between the two cameras for a few seconds and observed their timecodes in the lcd were the same.
I shot a wedding using the two cameras. Before the ceremony I recorded a laser pointer on both camera and then kept both cameras on during the entire wedding.
When I brought the avchd clips into the vegas 10 timeline, and followed their instructions, and spent two days finding the steps they forgot to list, and finally got it to sync up.
Compared to my laser point method, the auto sync was two frames off.
I am going to do a few more tests to determine why.