I have just found out that if I have HDMI cable plugged in and restart the laptop, a correct EDID gets picked up during boot process and I will have the native 1920x1080 available. So it seems the problem only exists if I plug in a HDMI cable when X has already started. See the Xorg.0.log below:
(II) intel(0): EDID for output HDMI1
(II) intel(0): Manufacturer: SAM Model: 509 Serial#: 1
(II) intel(0): Year: 2008 Week: 48
(II) intel(0): EDID Version: 1.3
(II) intel(0): Digital Display Input
(II) intel(0): Indeterminate output size
(II) intel(0): Gamma: 2.20
(II) intel(0): No DPMS capabilities specified
(II) intel(0): Supported color encodings: RGB 4:4:4 YCrCb 4:4:4
(II) intel(0): First detailed timing is preferred mode
(II) intel(0): redX: 0.640 redY: 0.330 greenX: 0.300 greenY: 0.600
(II) intel(0): blueX: 0.150 blueY: 0.060 whiteX: 0.312 whiteY: 0.329
(II) intel(0): Supported VESA Video Modes:
(II) intel(0): 720x400@70Hz
(II) intel(0): 640x480@60Hz
(II) intel(0): 640x480@67Hz
(II) intel(0): 640x480@72Hz
(II) intel(0): 640x480@75Hz
(II) intel(0): 800x600@60Hz
(II) intel(0): 800x600@72Hz
(II) intel(0): 800x600@75Hz
(II) intel(0): 832x624@75Hz
(II) intel(0): 1024x768@60Hz
(II) intel(0): 1024x768@70Hz
(II) intel(0): 1024x768@75Hz
(II) intel(0): 1280x1024@75Hz
(II) intel(0): 1152x870@75Hz
(II) intel(0): Manufacturer's mask: 0
(II) intel(0): Supported Future Video Modes:
(II) intel(0): #0: hsize: 1152 vsize 864 refresh: 75 vid: 20337
(II) intel(0): #1: hsize: 1280 vsize 800 refresh: 60 vid: 129
(II) intel(0): #2: hsize: 1280 vsize 960 refresh: 60 vid: 16513
(II) intel(0): #3: hsize: 1280 vsize 1024 refresh: 60 vid: 32897
(II) intel(0): #4: hsize: 1440 vsize 900 refresh: 60 vid: 149
(II) intel(0): #5: hsize: 1440 vsize 900 refresh: 75 vid: 3989
(II) intel(0): #6: hsize: 1680 vsize 1050 refresh: 60 vid: 179
(II) intel(0): Supported additional Video Mode:
(II) intel(0): clock: 148.5 MHz Image Size: 160 x 90 mm
(II) intel(0): h_active: 1920 h_sync: 2008 h_sync_end 2052 h_blank_end 2200 h_border: 0
(II) intel(0): v_active: 1080 v_sync: 1084 v_sync_end 1089 v_blanking: 1125 v_border: 0
(II) intel(0): Supported additional Video Mode:
(II) intel(0): clock: 85.5 MHz Image Size: 160 x 90 mm
(II) intel(0): h_active: 1360 h_sync: 1424 h_sync_end 1536 h_blank_end 1792 h_border: 0
(II) intel(0): v_active: 768 v_sync: 771 v_sync_end 777 v_blanking: 795 v_border: 0
(II) intel(0): Ranges: V min: 24 V max: 75 Hz, H min: 26 H max: 81 kHz, PixClock max 230 MHz
(II) intel(0): Monitor name: SAMSUNG
(II) intel(0): Number of EDID sections to follow: 1
(II) intel(0): EDID (in hex):
(II) intel(0): 00ffffffffffff004c2d090501000000
(II) intel(0): 30120103801009780aee91a3544c9926
(II) intel(0): 0f5054bdef80714f8100814081809500
(II) intel(0): 950fb3000101023a801871382d40582c
(II) intel(0): 4500a05a0000001e662150b051001b30
(II) intel(0): 40703600a05a0000001e000000fd0018
(II) intel(0): 4b1a5117000a202020202020000000fc
(II) intel(0): 0053414d53554e470a2020202020016f
(II) intel(0): Printing probed modes for output HDMI1
(II) intel(0): Modeline "1920x1080"x60.0 148.50 1920 2008 2052 2200 1080 1084 1089 1125 +hsync +vsync (67.5 kHz)
(II) intel(0): Modeline "1280x1024"x75.0 135.00 1280 1296 1440 1688 1024 1025 1028 1066 +hsync +vsync (80.0 kHz)
(II) intel(0): Modeline "1360x768"x60.0 85.50 1360 1424 1536 1792 768 771 777 795 +hsync +vsync (47.7 kHz)
(II) intel(0): Modeline "1152x864"x75.0 108.00 1152 1216 1344 1600 864 865 868 900 +hsync +vsync (67.5 kHz)
(II) intel(0): Modeline "1024x768"x75.1 78.80 1024 1040 1136 1312 768 769 772 800 +hsync +vsync (60.1 kHz)
(II) intel(0): Modeline "1024x768"x70.1 75.00 1024 1048 1184 1328 768 771 777 806 -hsync -vsync (56.5 kHz)
(II) intel(0): Modeline "1024x768"x60.0 65.00 1024 1048 1184 1344 768 771 777 806 -hsync -vsync (48.4 kHz)
(II) intel(0): Modeline "832x624"x74.6 57.28 832 864 928 1152 624 625 628 667 -hsync -vsync (49.7 kHz)
(II) intel(0): Modeline "800x600"x72.2 50.00 800 856 976 1040 600 637 643 666 +hsync +vsync (48.1 kHz)
(II) intel(0): Modeline "800x600"x75.0 49.50 800 816 896 1056 600 601 604 625 +hsync +vsync (46.9 kHz)
(II) intel(0): Modeline "800x600"x60.3 40.00 800 840 968 1056 600 601 605 628 +hsync +vsync (37.9 kHz)
(II) intel(0): Modeline "640x480"x72.8 31.50 640 664 704 832 480 489 491 520 -hsync -vsync (37.9 kHz)
(II) intel(0): Modeline "640x480"x75.0 31.50 640 656 720 840 480 481 484 500 -hsync -vsync (37.5 kHz)
(II) intel(0): Modeline "640x480"x66.7 30.24 640 704 768 864 480 483 486 525 -hsync -vsync (35.0 kHz)
(II) intel(0): Modeline "640x480"x60.0 25.20 640 656 752 800 480 490 492 525 -hsync -vsync (31.5 kHz)
(II) intel(0): Modeline "720x400"x70.1 28.32 720 738 846 900 400 412 414 449 -hsync +vsync (31.5 kHz)