Heat milk to 110°F to 115°F. Place in bowl of an electric mixer fitted with paddle attachment. Add yeast and 1 teaspoon sugar and let stand 5 to 6 minutes until foamy. Add remaining sugar, butter and eggs and beat until blended, about 1 minute. Change to dough hook attachment and add 3 cups flour. Beat on low speed 5 minutes or until dough is soft and pulls away from sides of bowl, scraping down sides of bowl and adding more flour if necessary.
Turn dough out onto lightly floured surface and knead 1 to 2 minutes or until smooth. Place in oiled bowl and cover. Let rise until doubled, about 1 hour.
Meanwhile, in a small bowl, toss together blackberries, sugar, lemon zest and cinnamons. Let sit 5 minutes. Mash with potato masher.
Line 9-inch cake pan with 2 long pieces of parchment paper leaving 4 to 5 inch overhang. Turn dough out onto lightly floured surface and roll to 16 by 10-inch rectangle. Spread blackberry mixture over dough within 1/2 inch of edges. Top with pecans. Roll up into log using long side of dough. Cut crosswise into 8 equal pieces and arrange in cake pan with 1 in center. Cover and let rise 1 hour or until about 1 1/2 times larger.
Preheat oven to 375°F. Bake 25 to 30 minutes or until deep golden brown. Meanwhile, whisk together confectioners' sugar, cream cheese and milk until smooth. Drizzle over warm buns. Let cool about 15 minutes before serving.
Note: If desired, you can prepare buns through rolling, cutting and placing in cake pan then let rise overnight in refrigerator. Remove from refrigerator about 1 hour before ready to bake in morning, letting buns come to room temperature.