Some part of the cooperation is on development of Africa which probabley is part of China's current plan or even part of OBOR. We know that Italy is major victim of the wave of iligle immigrants accross the ocean. An inductrialized and stable Africa is also in the interest of Italy. That could explain why Italy is more interested in OBOR than other Eurapian countries.
Does that make sense?
It’s much more likely after decades of poor economic management and a weak economy, Italy is willing to sacrifice some principles/accept some risk in return for Chinese investment in ports and businesses. China has invested heavily in Greece as well for the same reasons.
For one, borders are difficult for migrants to cross: trains and coaches near borders are often checked for migrants, some borders are under police surveillance (like between France/Italy), etc.
Second, Dublin agreements force migrants to apply for asylum in the first EU country that they give their fingerprints in (ie the one where they have their first encounter with police). Most migrants have fingerprints in Italy, Bulgaria, Hungary, Greece, Spain, ie the countries on the outskirts of Europe. So migrants can’t just walk to the country of their choice and claim asylum, as they will be “deported”, as a rule, to a country they explicitly don’t want to be in (Italy had high acceptance rates until recently but can offer no work, Hungary is known for extreme racism and violence against migrants, etc.)
Your (b) is on point though. Italy has been asking for a fairer distribution of migrants among the Member States for some time, but the most powerful Member States like their South/Eastern European moat a lot
But it's also easy to just keep walking to the country you want to be in since all the border controls are gone once you reach schengen area. Few easily avoidable exceptions. Further compounded by all these countries retaining their own asylum protocols, so even if a country is landlocked or access is limited by some other geographical feature, if you are able to show up then you are able to request asylum.