It's possible. Even if the modem chip is the same, you have to remember antenna design is a separate issue. I liken this to routers. Plenty of routers use the same Broadcom or Atheros chips, and they're roughly equal, but its a matter of antenna design and software and that separates the performance.
It's pure anecdotal evidence for me, but I've noticed that my Motorola Milestone (Droid 1) outperforms my Nexus S and GS2 in terms of reception. It also beat out my HTC Nexus One back in the day. I noticed faster GPS locks. I have not compared it to my Nexus 4 though. Perhaps Motorola has just maintained its ability to provide good reception on its phones. I've found that my 2 Samsung phones never performed that well either in terms of reception.