The "imposition" of the contract is only fairly recent and very importantly was AFTER the strike vote, and therefore can't be a reason. The BMA have agreed with most of it, so does that really justify a strike? It's possible that a lot of it can effectively be imposed by getting the employers to change the rosters. As the current contract is "looser" on working hours there is plenty of scope to move thing around and all without the 13.5% increase.
Concessions have been made by Jeremy Hunt, eg extra Saturday pay where they have already worked one Saturday that month, increase in basic pay up from 11% to 13.5%. A sticking point seems to be that the BMA insist on doctors get pay rises and advancements based on time served, including long-term sick leave and maternity leave. This is not shelf stackers we're talking about, career advancement should be based on ability shown and actual amount of experience dealing with actual patients. How would it be fair or equitable(ie equal) for a person who has spent 2 out of the last 6 years at home, being "ahead" of somebody who has worked solid for 5 or 6 years? You see on medical dramas that junior doctors need to have real world experience of various medical procedures in various circumstances. Medical school is unable to fully prepare them in that way. They don't come out fully fledged and ready to go.