“To the best of my knowledge there is no Shader Model 3.0a or Pixel Shader 3.0a specifications,” Richard Huddy, European Developer Relations Manager, ATI told X-bit labs. “I suppose it’s also conceivable that MS might want to designate the Xbox 360 pixel shaders as ‘PS3.0a’.”More details at X-bit Labs
ATI denies R520 Pixel Shader 3.0a rumours

ATI denied that it's R520 graphics core would feature support for Pixel Shader 3.0a specification. This was rumoured last week by some websites.