Ah misread that a bit. The code won't help, so ignore that.

Actual answer: It depends on where you evaluate the code.

irb(main):001:0> class A
irb(main):002:1>   def self.method_added( sym )
irb(main):003:2>     p "A##{sym}"
irb(main):004:2>   end
irb(main):005:1> end
=> nil
irb(main):006:0> class B
irb(main):007:1>   def self.method_added( sym )
irb(main):008:2>     p "B##{sym}"
irb(main):009:2>   end
irb(main):010:1> end
=> nil
irb(main):011:0> d = Proc.new{  def x; end }
=> #<Proc:0xb79d553c@(irb):11>
irb(main):012:0> A.class_eval &d
"A#x"
=> nil
irb(main):013:0> B.class_eval &d
"B#x"
=> nil