Was the master cylinder replaced by the dealer? Did the lights come on immediately after the repairs, a few days later, a week? Did they run a diagnostic with the scan tool when you brought it to the dealer, if so; what were the fault codes they read out?
Yes, the car is perfectly safe to drive as is. With the ABS and traction warnings on; you will not have anti lock brake or traction control intervention, that is the only side effect. The braking system operates normally with these lights on. Sounds to me like you may need to replace the ABS module to rectify the lights if you feel you need to venture that road in the future.
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Thanks and good luck,
It depends on what they need to replace for the rebuild, I know a lot of online companies can program the module in house, so no dealer trip is needed; essentially plug and play.