To the OP's question. Yes it can, in fact most strong racers do thier significant training sessions solo. If you are looking to hit specific power/duration goals on a given ride that is hard to do in a group.
To the nerd fight. There is a semantic issue with cycling and strength. Agree with asgelle the actual forces involved at say 300W are minimal. Comparable to even a body weight squat. I've seen more descriptive terms used, "muscular endurance" or the one I like "fatigue resistance", to describe the training impact of what some posters are calling strength. Stuff like standing reps, big gear work, etc can be very adaptive & have an impact on your cycling ability. But they are not creating leg strength above a pretty low threshold.
Throwing sprint numbers around I haven't lifted in 20 years, still hit 1200W & change max at 62 and don't feel I'm particularly "strong" in the true sense of the word.
Last edited by Voodoo76; 09-14-18 at 06:13 AM.