You didn’t use the same names:

~~~scala
Welcome to Scala version 2.11.0-RC1 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0).
Type in expressions to have them evaluated.
Type :help for more information.

scala> object A { implicit class dsl(val x: Int) { def A = 42 } }
defined object A

scala> object B { implicit class dsl(val x: Int) { def B = 43 } }
defined object B

scala> import A.dsl
import A.dsl

scala> 1.A
res0: Int = 42

scala> import B.dsl
import B.dsl

scala> 1.A
<console>:13: error: value A is not a member of Int
              1.A
                ^
~~~

So, we will have to go with the `Implicits` nested object and unique names :-(