Can the contents of a partition be recovered after partition table is overwritten?
Quick and Simple: Since it's a GPT disk you can run gpart recover /dev/disk1 to fix the table. You blew away the first ~700MB of the drive, so any partitions touching that area are gone too (more or less). The rest of the disk should be fine. I'm not sure if OSX comes with gpart, so you may need to download it somewhere.

The longer details: Concerning the partition(s) that were only partially overwritten, some of the files may be recoverable. The tools to do so are much more complicated and you'll be wanting to find someone who really knows what they're doing for this. If you're concerned with any of these files don't even try anything except unplugging the drive. Also, the overwritten data can probably be recovered by a data recovery service, but this would cost tens of thousands of dollars.

Also, if this was a MBR disk you'd be completely hosed unless you happen to know the exact size and offsets of all partitions. This information can be printed from fdisk, but it's best to simply not make mistakes like this.