That seems to have been a common practice on the Soo Line. Every extant 1913,13,15 Soo boxcar I've looked at has trucks with Andrews sideframes with CB&Q cast in; the cars were built with Bettendorf "T" section sideframes, and when those were banned from interchange service, the Soo had to come up with something to keep the cars on the road, and apparently purchased sideframes from cars the Q was scrapping.

Did the foundries have a minimum order quantity for personalized parts?
The 10 Brill Master Unit trolley cars built by J. G. Brill Co. for Philadelphia & West Chester Traction Co. about 1930 have folding step castings personalized for B&QTC (Brooklyn & Queens Transit Co.)!