Yes they can. The two Rikers was the result of an accident during an attempt to cope with a high-risk beaming scenario. Here's the technobabble.And you really see the Federation. With its love for life and it's utter hatred for cloning to be simply okay with killing and cloning millions a day? That wouldn't make any sense. Let alone that we could simply "resurrect" people from the transporter buffers and create a new Neelix and Tuvok so that Tuvix doesn't have to die.
...
How would you explain the two rikers then? They can't both be the original one.
In other words, it was an accident.RIKER: You wanted to see me, Mister Data?
DATA: Yes, sir. It appears we will be able to transport to the surface sooner than anticipated.
RIKER: Is the planet's distortion field re-phasing sooner than we predicted?
DATA: No, sir. Using the Potemkin's transport logs from the original evacuation, Commander La Forge and I were able to modify the transporters.
RIKER: So we can beam through a higher distortion field.
DATA: The transporters are considerably more efficient than those used on the Potemkin eight years ago.
RIKER: That's a good thing. I almost didn't make it off the surface. When can we get started?
DATA: Ninety seven minutes, sir.
RIKER: How long will the transport window be open?
DATA: Twenty six minutes. After that, the distortion field will re-phase.
RIKER: That doesn't give us much time to retrieve the database.
DATA: The planet's proximity to its sun will create two additional transport windows in the next three days.
RIKER: Let's hope that's enough.
DATA: It will have to be, sir. The next transport window will not occur for another eight years, when the planet's orbit will bring it close enough to the sun to de-phase the distortion field.
[...]
LAFORGE: Apparently there was a massive energy surge in the distortion field around the planet just at the moment you tried to beam out. The Transporter Chief tried to compensate by initiating a second containment beam.
DATA: An interesting approach. He must have been planning to reintegrate the two patterns in the transport buffer.
LAFORGE: Actually, it wasn't really necessary. Commander Riker's pattern maintained its integrity with just the one containment beam. He made it back to the ship just fine.
CRUSHER: What happened to the second beam?
LAFORGE: The Transporter Chief shut it down, but somehow it was reflected back to the surface.
PICARD: And another William Riker materialised there.
RIKER: How was the second pattern able to maintained its integrity?
LAFORGE: The containment beam must have had the exact same phase differential as the distortion field.
RIKER: Which one of them is real?
LAFORGE: That's the thing. Both. You were both materialised from a complete pattern.
CRUSHER: Up until that moment, you were the same person.
PICARD: But of course, as you and Lieutenant Riker have lived very different lives for the past eight years, you are now very different people. I suppose it's a little like meeting someone's twin. But no matter how strange it may seem to us, we now have two Will Rikers on board. And as Lieutenant Riker will be with us for several days, I think we should do everything we can to make him comfortable and welcome.
I agree completely with Orphalesion, there.