It wouldn't do anything to alter scope without contract changes, at least per the East contract and transition agreement. The language doesn't specify who can fly the bigger RJ's for Express, only that a certain number can be flown (see Repbulic's E175's for another Express operator of large RJ's). Mesa is a mess financially - only the fee for departure contracts are keeping them afloat for now since everything else is losing money (well, excepting any EAS routes they have). The only positive about buying them that I can see is that they're cheap. The stock closed at 24 cents per share Friday. But on the other hand all you get if you buy them is debt and a bunch of leased or mortgaged airplanes, many of which are smaller RJ's that US doesn't need. Probably the most valuable thing Mesa has is an operating certificate.
Of course, put all that together and it may sound like a good idea to fiddle-de and fiddle-dumb...
Jim
I wonder how that press release would go.........
F. Forrest Gump (executive vice president US Airways) announced to day that US Airways will acquire MESA airlines. The US Airways executive team are also pleased to announce another BOHICA payout for current US Airways employees due to the acquisition of MESA. A 5% off coupon for Cold Stone Creamery and a TSA compliant trial size package of "Preparation H". Our employees should be able to get great value from this current BOHICA payout. "What the don't eat they can sit on".
Jonathan Ornstein has been named Executive Vice President of Draconian Labor Rules and Exploitation.
We are also happy to announce that ALL MESA pilots will remained employed. The company has agreed to the seniority list submitted by the MESA pilot group and RALPA Regional Airline Pilots Association.
Pilots on the list will immediately be able to immediately hold Positions on the A330 INTL on the merged seniority roster. Their class dates will be based solely on current attrition rates or how fast the current pilot group dies off. Any delay is due to technical issues since the A330 training modules have not been released for MS Flight SIM - the company is now looking for additional training centers in India, Nicaragua, and the Philippines that utilize XBOX or ATARI technology."
Flight Attendants will be eliminated our New "A train" configuration for the "A(ir) BUS",
Aside from luxurious bench seating in Envoy Class we will begin offering offering SRO CLASS (standing room only) in economy - each will be provided with their own Imitation Leather stabilization strap.....to keep after the flight ......for an additional $15.00.
The Mesa name will be retired. And US Airways will be changing our name to
"Mesa Grande by US Airways" 
Just Imagine.......
One thing for sure - if it results in Jonathan Ornstein becoming a victim of the current economy by being put out on the street....It can't be too bad a scenario.
Unfortunately we already have his clones running this operation.
