Yes. Regardless of whether the array is hardware RAID or software RAID, it's a block device and that's all dd needs.
If it were software RAID, then really this ghosting would only be suitable for making a backup. It won't be bootable or anything, because the block device in question wouldn't include any of the actual disc's mbr's or partition tables.
Since it's hardware RAID, then it's possible you may get some functionality out of it. With (true) hardware RAID, the RAID array looks just like a normal hard drive to the OS. The MBR, partition table, etc...as far as anything other than the RAID hardware is concerned, the array is just a single hard drive.
As I understand it, not all "hardware" RAID is true hardware RAID, though.