I notice that the lateral is open to everyone, but my question is, if you are coming from a non-law enforcement rating, would you be sent to the ME "A" school and have to go back to being a third class.

1). Dont believe anything you read on here

2). No. If you are accepted for lateral, you will become an ME becuase your package demonstrated you had enough skills to be intitially in the rating. If you do not, you will not be accepted. THEN you could attempt a normal change of rating process and ask to change ratings via A-School.

The issue I have with this process is that even if you get picked up to lateral over you will still have to complete your tour at your current paygrade and rate. In my case that would be 2 years as an ME doing MK work. That doesn’t make any sense to me. If the jobs are open why not start to plug those that lateral over into the jobs starting shortly after Jan 2010?

The "jobs" aren't really open. They are still filled by the members assigned to that unit, Its not like they made a bunch of new positions, they just simply "renamed" them as ME billets.
I know they say not to expect to transfer until the end of your tour... and NO ONE should think otherwise. However, once these people currently in the positions that did NOT lateral to ME begin to transfer out, they will need MEs to come in and fill those positions.
The process is the way it is. Its really the only way they could do it to ensure that units aren't effected by people choosing to lateral.