Work with tf data timestamped from bag file

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I am replaying a bag file containing point clouds, and right now can only work on that bag file.

Now rosbag play publishes the data with the original time stamps, which makes sense.

However this makes working with tf somewhat difficult, since a tfBuffer.lookupTransform at ros::Time::now() with any reasonable duration obviously gets me an empty buffer and any ros::TimerEvent last_real also returns the Unix Epoch, which does not directly translate to the timestamps from the bag data.

What is the proper way to handle Timestamping differences like this? How can I efficiently work on the data, just like it is from a real-world, live robot?