Are voice, text and data shared the same channel in 2G, 3G and 4G networks?
2G networks handle voice and data separately. Voice is on the TCH traffic channel. GPRS data on PDTCH. SMS isn't really treated as either, and is on the SDCCH control channel. 

3G voice and data are both on DCH/DTCH, but using different quality of service classes. Or for HSPA, HS-DSCH and E-DCH. 

LTE and VoLTE both use PDSCH/PUSCH, but there are some new scheduling options for volte like semi-persistent scheduling and packet aggregation.