if you deduce that from “no answer”, it means you are quite lazy 🙂
most vendors have a re-useable approach when it comes to BSS and NSS HW, from 2G to 4G. The softwares too are usually compatible.
Ericsson does have an advantage regarding their HW, and it seems like they had the clearest vision right from the start… or maybe they just were very advanced in their hw design, compared to all the others.
But their O&M SW is a pure nightmare… So all the money you saved by “reusing” the 2G/3G HW for 4G evolution, you may actually lost in operating & supervising costs 🙂 (i may be a little dramatic…)