The results were a bit surprising, and they seemed to reveal some of the history of the house itself. We already knew that the gas line was put at some point after the house was originally built, but it seems that it didn't come in until after the garage was built as well. In fact, based on the long route that the electrical wire took, it looks like they originally planned to attach the garage to the side of the house, but then later built the larger garage at its current location. Once they built that garage and decided to heat it with a gas furnace, they no longer needed to keep that side of the house free of underground cables, so they made a beeline (and a shallow one) from the back of the house to the garage wall with the heater.
Our electrician also pointed out that our current master bedroom was probably the original garage to the house. I had not considered the idea before, but it certainly makes sense when looking at a number of quirks in the house design. I'd really be interested to see the house and property at its various stages of development.
At least we now know where the lines head should we have any digging projects in the future.