They probably sniffed out the originating BTN which when it goes to these services is different than your phone number.

Remember they don't "always" get your caller ID at Google, they get the ANI from either Voipo or Level3 which could be the same number each time or it could be distributed on an outgoing basis, so they are doing this so certain companies don't flood the with free DA requests (along with the option to be connected for free).
My tests to an ANI service testing point that I used to use when I worked for one of the big Telco's revealed the following:
1. test one - my correct number was displayed
2. test two - 319 228-9999 was displayed
3. test three - my correct number was displayed
4. test four - 319 228-9999 was displayed
5. test five - 319 228-9999 was displayed

So it seems that perhaps Google has the 319 number flagged in its system to be "ignored".