I've read about it being done in the RC literature.  There can be start-up problems: the ESC needs to know where the motor is to work correctly, with two motors it can get confused.  The people that write about doing it say "just try coming off of idle, and if the motors don't start up then go back and do it again".

So it's probably something that would work if you were running throttle control, but not something you'd want to try at all with a timer.

And, but, etc.:

I haven't seen it mentioned for years, you need an ESC with double the current capacity than what you'd need for each motor, so while you're going to save some bucks by having one big ESC instead of two little ones you're certainly not going to save the price of one little ESC.  And you're going to need to run long wires to each motor from your central ESC, and you must have one central battery instead of one in each nacell (or whatever), etc.

Etc., etc.

I wouldn't do it, personally, except maybe on a bet.

Hello Jim,
Short answer ... NO.
    Dean P.

I'll answer for Dean, then he can elaborate:

An electronic speed control for a brushless motor does, indeed, pulse the three wires in sequence to make the motor turn.  In order to do this correctly it needs to know where the motor is.  There's always one motor wire that's not connected, and the ESC figures out the motor position by watching the voltage on that wire.

The problem with running two motors on one ESC is that the synchronization between ESC and motor is an all-or-nothing proposition: if the ESC is in sync with the motor then the motor produces torque that's always in the same direction and everything is fine.  If the ESC isn't in sync with the motor then the motor still produces torque -- but that torque spends as much time fighting the motor rotation as it does aiding it, so the motor acts like it's not getting any voltage at all (well, except for the loud noises, heat, and possibly smoke).

Back when brushless motors were new and ESCs were expensive, some hearty souls did, indeed, run multiple motors off of one ESC.  They sometimes even worked fine.  If it's going to work, it'll be because the two motors happen to come up in synchronization, and because they happen to stay that way during flight.  But I haven't heard about anyone doing that sort of thing for years, and I have only heard about it being done on RC craft, where the pilot can monitor the motor performance and shut things down if necessary.  I really think that trying to do this on a timer would lead to disappointment at best, and most likely to ruined equipment.

It's actually much simpler with brushed motors: in that case the ESC just acts like a variable voltage to the motors, which take care of powering up the right windings mechanically (that's what the brushes are for).  So if you had brushed motors you could just connect them in parallel and run them off of a single ESC of sufficient ratings with no problem.

So: you really, really don't want to try this.  One extra ESC costs more than two, and two extra ESCs is what you'd be buying after you burnt up the first one up trying to make it power two motors.  So get that one extra ESC now, and save money.

Thanks, Tim!
Like John said, one battery shared between the two is fine, so is one timer shared between the two ESCs but you need two ESCs.
Getting two motors to start and stay in lock is an unacceptable crap shoot, and a bad start on one side could even fry the electronics.
By the way, if and when you run one timer into two ESCs, remember to cut the red or power wire on one leg of the "Y" style servo cable so that the timer runs from the 5V supply on one of the ESCs, rather than shorting both 5V supply outputs together.

Dean