Well-to-Wheel (WtW) CO2 emissions of different powertrain topologies employed to power a medium duty truck are analyzed in this paper. The analysis covers topologies of the parallel and the series plug-in hybrid electric vehicles (PHEVs), which are driven according to different strategies of depletion of the electric storage devices (ESs). These results are benchmarked against results of conventional internal combustion engine vehicles (ICEVs). The Tank-to-Wheel (TtW) data are obtained by a forward facing vehicle simulation model, whereas Well-to-Tank (WtT) analysis covers CO2 intensity of the Diesel fuel and four different realistic CO2 intensities of electric energy production. To ensure comprehensiveness of the study vehicles were also operated according to two drive cycles that feature significantly different velocity profiles. In addition, influences of different control strategies of powertrain components were also analyzed. This broad portfolio of scenarios reveals insightful WtW CO2 emissions guidelines for introducing plug-in hybrid electric trucks to different regions. The results indicate that the propulsion electrification in medium duty trucks has, in comparison to passenger cars, a smaller potential for reduction of Well-to-Wheel CO2 emissions because of the higher efficiencies of the internal combustion engine in such trucks. Results of this study were also used to identify the threshold value of the CO2 intensity of electric energy production that favors the operational switch from Charge Depleting (CD) to Charge Sustaining (CS) mode. Additionally, it was shown that for longer recharge intervals, operation in the blended mode with less intensive depletion rate of the ES can feature lower WtW CO2 emissions of the PHEVs.