It is possible. However, considering that it would only take one person being exceptionally curious with IDA, one employee to blow the whistle (the source is still "open" to a fairly large number of people, and a backdoor is far harder to hide than passive collection of existing data), or one slipup to cause a massive amount of PR damage, and this has never occurred, nor does the Snowden leak suggest this is happening, I personally consider this claim extremely improbable. YMMV.