I know both the allies and central powers sought for Italy's allegiance during the war, but what were its political ties immediately before that? Had Germany tried to convince them to work together before the outbreak of conflict? Was the border between Italy and France highly fortified? And would this have stopped Britain from immediately joining the conflict?
I'm not a WWI specialist, but maybe I can help! Apparently it was part of the initial plan of a war versus France, but it was abandoned circa ten years before the start of WWI.
Italy was since 1882 a member of the Triple Alliance with Germany and Austria-Hungary. It was a defensive treaty, which explicitly considered the case France attacked Italy or Germany, and wasn't valid against the UK.
Over the years, the Triple Alliance suffered for dissatisfactions between the parts and was several times modified, while Italy got in better relations with the UK and France, the ancient colonial rival.
In 1902 a secret pact assured the neutrality of Italy in case of a war between France and Germany, even if France had attacked first under German provocation. Meanwhile, the relations with Austria precipitated. A clause in the Triple Alliance acknowledged the interests of both Austria-Hungary and Italy in the Balkans, so that an expansion of one power there would have to be recompensated to the other.
In 1914 the Habsburg ultimatum to Serbia happened with the consent of Germany, but without consulting Italy. That was seen as a violation of the pact and separated further the two allies. When Austria-Hungary declared war on Serbia, the Italian government chose neutrality for it was not a defensive war.
In the first draft of the Schlieffen Plan, Aufmarsch West I, apparently the Germans expected an isolated French-German war, with a possible help from Italians and Austro-Hungarians via the Italian border.
As time went by, relation within the Alliance worsened; even if the Italo-French pact was secret, Germany had expected Italian neutrality in case of a great war, especially if the UK had joined; so the German commanders prepared Aufmarsch West II, not including the Italian front.
Even after the outbreak of war, Germany and Austra-Hungary tried to convince Italy to mantain an (amicable) neutrality rather than to join the war to their side.
I don't know of the French-Italian border fortifications.
About the UK, I don't think the Italian intervention with the Central Powers would have stopped them. On the other way round: the fear of a British blockade on the Mediterranean Sea was one of the reasons Italy was recalcitrant to join the war with its allies.
Italian Wikipedia has quite detailed information about Italian neutrality and Triple Alliance Treaties.